In contrast to the walls mentioned in the last halachah of the previous chapter...

[There are requirements regarding] the s'chach of a sukkah, and not all substances are acceptable [to be used for this purpose]. - Some of the requirements mentioned by the Rambam were established by Torah law, while others are Rabbinic ordinances, as explained below.

For s'chach, we may use only a substance which:

a) grows from the ground - i.e., is an agricultural product and is neither found naturally - e.g., metals - nor produced from animals nor manufactured synthetically;

b) has been detached from the ground - and is not still connected to its source of nurture;

c) is not subject to contracting ritual impurity - This excludes articles used as food and those that have been fashioned into utensils. These three requirements are alluded to by Deuteronomy 16:13: "Make the Sukkot holiday for yourselves for seven days, when you gather in from your grain and grapes..."

Sukkah 12a explains that the verse implies that the s'chach, the essential element of the sukkah, must resemble "the leftovers from the grain and grape harvest."

(The expression "alluded to" was used rather than "derived from" on the basis of the Rambam's commentary on the Mishnah, Sukkah 1:4. That expression implies that the concept cannot be derived from the verse per se. Rather, it was transmitted as a halachah l'Moshe miSinai, and the Biblical verse is merely an allusion.)

The Rambam gives examples of entities which are not acceptable as s'chach on the basis of these principles in the following halachah.

d) does not have an unpleasant odor - As implied by the following halachah, this and the following clause are Rabbinic decrees. S'chach with an unpleasant odor will not create an inviting holiday environment. Indeed, substances with an unpleasant odor should not be used for the sukkah's walls either.

e) and does not have elements which fall off and wither constantly - for a person will not be pleased to have portions of the s'chach falling into his food. The Mishnah Berurah 629:39 states that the prohibition applies to elements that fall off naturally. However, if they fall off only when subjected to wind, there is no difficulty in using them.

When a person uses as s'chach a substance which does not grow from the ground, is still connected to the ground, or is subject to contracting ritual impurity, [the sukkah] is not acceptable. - for these requirements stem from the Torah itself. The particular aspects of these requirements are described in this and the following halachot.

However, if he transgressed and used as s'chach a substance which has elements which fall off and wither - Sukkah 13a gives the shrub known as hollow as an example of such a substance.

or possesses an unpleasant odor - Sukkah 12b gives the plant known as wormwood as an example of such a substance.

it is kosher - after the fact, for these are only Rabbinic requirements. The Mishnah Berurah 629:38 emphasizes that even if other s'chach is available, there is no need to remove the s'chach with the unpleasant odor. However, the Pri Megadim stresses that if the odor is so unpleasant that no one would bear it in his home, it is forbidden to use such a sukkah.

[Our Sages] - Sukkah 13a

said only that one should not use these as s'chach lest one leave one's sukkah and depart.

One must take care that the branches and leaves should not descend within ten handbreadths of the ground - the minimum height for a sukkah prescribed in Chapter 3, Halachah 1.

so that one will not be uncomfortable - Sukkah 4a describes this as "a disgusting dwelling, unfit for human habitation."

when using the sukkah. - The Rambam's phraseology leaves room for the interpretation that this is a suggestion, but not an absolute requirement. (See Rabbenu Manoach.) Nevertheless, the Shulchan Aruch (Orach Chayim 633:9) states that such a sukkah is unacceptable for use.

If one used metals - even if they have not been made into utensils, but are still in a raw state in which they are unfit to contract ritual impurity;

bones, or hides - even if they have not been made into garments, but are still in a raw state in which they are unfit to contract ritual impurity;

as s'chach, it is unacceptable, because these do not grow from the ground.

If one suspended vines and the like over it until they made a sukkah, it is unacceptable, because they were not uprooted [from the ground]. - The laws governing the use of such plants as s'chach after they have been hung over the sukkah and then detached from the ground are discussed in Halachah 12.

Should one use wooden utensils - In particular, this refers to wooden utensils that have a receptacle or are wide and other articles are frequently placed upon them - e.g., a table. However, wooden utensils that do not fall into these categories are not subject to contracting ritual impurity, and, hence, may be used for s'chach. An example of such utensil is a ladder. The Rambam (Hilchot Keilim 4:1) declares that a ladder is not subject to contracting ritual impurity. Hence, according to his opinion, there is no difficulty with using it as s'chach.

(It must be emphasized that other authorities question the Rambam's decision on a ladder and maintain that a ladder may be subject to contracting ritual impurity. Hence, it is preferable not to use it as s'chach. See the Shulchan Aruch and Ramah, Orach Chayim 629:7.)

mats that were made to lie on - However, mats that were made for use as s'chach or for shade may be used as s'chach. Halachah 6 discusses the laws which apply when a mat was made without any specific intention.

and the like as s'chach, it is unacceptable, because they are subject to contracting ritual impurity. Similarly, using broken - e.g., utensils with holes of sufficient size to render them no longer subject to contracting ritual impurity. (See Hilchot Keilim, Chapter 6.)

and worn out - e.g., garments that have worn out and are less than three fingerbreadths by three fingerbreadths in size and, hence, are no longer subject to contracting ritual impurity (Sukkah 16a; Hilchot Keilim 22:21).

utensils as s'chach is unacceptable. - This is a Rabbinic decree on the basis of the following rationale...

Since these substances were subject to ritual impurity - previously,

[the latter law was instituted] lest one use broken pieces - from utensils

which have not yet attained a state of [unquestionable] purity - i.e., are still subject to contracting ritual impurity.

as s'chach.

If one used foods - This refers only to foods for humans. Food which is eaten primarily by animals is not subject to contracting ritual impurity (Hilchot Tum'at Ochlin 1:1) and hence may be used as s'chach (Taz 629:12).

as s'chach, it is unacceptable, because they are subject to contracting ritual impurity. - There is a slight imprecision in the Rambam's statements. Produce is not subject to contracting ritual impurity until it comes into contact with liquid. (See Leviticus 11:38; Hilchot Tum'at Ochlin 1:1-2.) Nevertheless, foods are not fit to be used as s'chach even though they have never come into contact with water (Shulchan Aruch HaRav 629:1; Mishnah Berurah 629:28).

[When one uses] branches from a fig tree which contain figs, runners from a grape vine which contain grapes, branches of a date palm which contain dates and the like - i.e., the difficulty being that although the branches are proper s'chach, the fruit is unfit to be used for that purpose...

[the following rules apply:] We see if the waste - the branches and leaves

is more than the food - the fruit

then we may use them as s'chach. If not, we may not use them as s'chach. - Rabbenu Manoach explains that these decisions are based on the principle that according to Torah law, mixtures are categorized according to the majority (בטל ברב).

On the basis of Sukkah 13b-14a, the Shulchan Aruch (Orach Chayim 629:10) explains that sometimes the stems of the fruit are considered part of the fruit, and on other occasions part of the branches. The Magen Avraham 629:12 explains that generally, a stem is not considered to be longer than three handbreadths. However, there are certain instances (e.g., grains) when a longer measure is considered. Hence, it is proper to be stringent in this regard. (See also Shulchan Aruch HaRav 629:15-16.)

The apparent contradiction between this halachah and Halachah 13 is discussed in the commentary on that halachah.

If one uses as s'chach vegetables - The Maggid Mishneh explains that this refers to vegetables that are used as animal food, and hence were not excluded by the previous clause of this halachah. Rabbenu Manoach and the Shulchan Aruch (Orach Chayim 629:12) explain that this refers to vegetables that are eaten by humans. Sukkah 13b appears to support the latter interpretation, stating:

The vegetables with which a person can fulfill his obligation on Pesach... [can] invalidate a sukkah, [because they are considered] to be vacant space.

which, when they dry up, will wither, and none of their substance will remain - i.e., the vegetables will dry up and wither during the Sukkot festival, leaving the sukkah with more vacant space than shade (Kessef Mishneh).

even though they are now fresh, their place is considered to be vacant, as if they did not exist. - According to the Maggid Mishneh's interpretation, the explanation of the law is straightforward. It teaches us that rather than consider the vegetables to be non-kosher s'chach, we consider their space to be vacant. The latter interpretation requires a slightly more intricate explanation. The vegetables are not considered to be non-kosher s'chach, which would invalidate the sukkah if they take up four handbreadths, as explained in Halachah 14. Rather, their space is considered to be empty. Hence, a space of three handbreadths is sufficient to invalidate the sukkah, as explained in Halachah 20.

If one used as s'chach branches of flax which were not crushed and combed, they are kosher, because they are still considered to be wood. - The use of the word עץ, rendered as branches or wood, with regard to flax, has its source in Joshua 2:6, which describes how Rachav "hid them in branches of flax."

After the flax has been crushed and combed - The Rishon Letzion questions the law when the flax has been crushed but not combed, and concludes that as long as it has not been combed, it is acceptable. Nevertheless, Shulchan Aruch HaRav 629:5 does not accept this conclusion.

it may not be used as s'chach - Though it is not considered to be a garment and, hence, is not subject to contracting ritual impurity (Maggid Mishneh; see also Shabbat 27b), it may nevertheless not be used as s'chach...

since its form has changed and it is as though it is no longer a product of the earth. - The Ra'avad disagrees with this principle and states that even before it is woven into a garment, flax is useful to stuff pillows and covers. Hence, it is subject to contracting ritual impurity and is thus unfit to be used as s'chach.

The Maggid Mishneh points out a contradiction to the Ra'avad's logic. The "male arrows" mentioned in the following halachah are - like flax - prepared to be used for a purpose. Nevertheless, they are considered acceptable for use as s'chach.

Rav Kapach mentions two possible extensions of the difference of opinion between the Rambam and the Ra'avad:

a) paper or carton - According to the Rambam, it may not be used because it no longer resembles a plant produced from the earth. According to the Ra'avad, it might be acceptable, since it is not subject to contracting ritual impurity.

b) cotton wool - It may be used for the purposes mentioned by the Ra'avad and thus, according to his opinion, would be subject to contracting ritual impurity. Nevertheless, its natural form is preserved. Hence, according to the Rambam's opinion, it would be acceptable. (It must be noted that the Magen Avraham 629:3 and Shulchan Aruch HaRav 629:5 maintain that after cotton has been combed, it is considered as though its form has been altered.)

One may use ropes made from palm bast or hemp and the like as s'chach, since their original form is unchanged and ropes are not considered to be utensils. - nor are they subject to contracting ritual impurity. The Shulchan Aruch, Orach Chayim 629:5 quotes this law as halachah, but adds that ropes of flax and canvas may not be used for this purpose.

[The following rules apply] when one uses arrows as s'chach. - The question whether the arrows are acceptable as s'chach or not revolves around another issue - their susceptibility to contracting ritual impurity.

Those which are "male" - i.e., the end of their body is sharpened and comes to a point, which is intended to be put inside a metal arrowhead.

are kosher - for the arrow itself is considered a simple wooden utensil which is not susceptible to contracting ritual impurity. (See Hilchot Keilim 1:10.)

The Magen Avraham 629:2 states that this decision applies only before these arrows were placed in the arrowhead. If they have been placed in the arrowhead, even if subsequently removed they are no longer acceptable as s'chach.

those which are "female" - i.e., the end of their body is hollowed out for the arrowhead to be inserted within

are not acceptable. - for they are subject to contracting ritual impurity.

Even though [ultimately,] they will be filled with iron - Hilchot Keilim 2:3 states: "A receptacle which is made to be filled is not considered a receptacle." Thus, one might assume that these arrows would also not be considered as having a receptacle. The Pri Ha'aretz explains that since the iron arrowheads are often removed from these bodies, it is considered as though...

they have a receptacle. Hence, they are susceptible to contracting ritual impurity, as are all utensils with receptacles. - It must be noted that Rashi and other commentators follow the simple interpretation of Sukkah 12b (the source for this law) and disagree with the Rambam's decision in Hilchot Keilim. They maintain that if a utensil has a receptacle, even if it will be permanently filled, it is subject to contracting ritual impurity.

A mat of reeds, of raw rubber, or of hemp - if it is small, we may assume that it was made to lie on. - The commentaries note an apparent contradiction in the Rambam's words. Hilchot Keilim 25:13 states that even a small mat of reeds or hemp is not subject to contracting ritual impurity, because it is uncomfortable to lie on.

Therefore, it may not be used for s'chach unless it was [explicitly] made for this purpose. - Since the mat was made with that specific intention, we do not follow the general principles, but rather judge it individually.

If it is large - The Rambam's statements are based on Sukkah 20a. It must be noted that his decisions are dependent on the version of the text of the Talmud he accepted. The Ra'avad and others interpret the word גדולה as related to the word גדיל (tassel). Thus, they explain that the Talmud is referring to a small mat. However, because it is made of thick tassels, rather than woven, it is not comfortable to lie on, and hence would most likely be used for shade. According to this opinion, any woven mat, even if it is large, is unfit to be used as s'chach. The Shulchan Aruch (Orach Chayim 629:6) quotes the Rambam's interpretation.

we may assume that it was made for shade; therefore, it may be used for s'chach unless it was [explicitly] made to lie on. - The Ramah (Orach Chayim, ibid.) mentions that in places where it is customary to affix mats permanently as the roofs for homes, they may not be used for s'chach. The Rabbis instituted this decree lest people remain in their homes on Sukkot without differentiating between them and a sukkah.

If it has a border - a small lip (Sukkah 20b)

even a large mat may not be used as s'chach, because it is considered to be a receptacle. - Tosafot, Sukkah 20b quotes Ketubot 50b, which explains that such mats were used to collect dates.

Even if the border was removed, it may not be used as s'chach, because it would be considered to be a broken utensil. - which, as explained in Halachah 2, may not be used as s'chach even though they are not susceptible to contracting ritual impurity.

Boards which are less than four handbreadths wide - In many places throughout the Talmud, four handbreadths is established as the minimum size of an area. Hence, a board of that size is considered significant and may not be used as s'chach (Sukkah 14a).

may be used for s'chach even though they have been planed - smooth, and thus are fit to be used in their present state (Sukkah 15a; Rabbenu Manoach).

If they are more than four handbreadths wide, they should not be used as s'chach, even though they have not been planed. This is a decree [instituted] lest one sit under a roof and regard it as a sukkah. - A person might think: "What is the difference between the sukkah and my house - they are both covered with boards?" This is surely a false assumption. As explained in the following halachah, since the boards of a roof were not placed there for the purpose of shade, but rather to be part of the permanent structure of the house, they cannot be considered to be s'chach (Sukkah 14a; Rabbenu Manoach).

If one placed a board which was more than four handbreadths wide over [a sukkah, the sukkah] is kosher. - The Maggid Mishneh explains that this applies only when the board is placed at the side of the sukkah. Thus, it could be considered to be an extension of the wall (דופן עקומה), as explained in Halachah 14. However, if it is in the midst of the sukkah, it is not acceptable. The Kessef Mishneh explains that this law can apply even in the midst of a sukkah, provided the sukkah already possesses its minimum size. His decisions in the Shulchan Aruch, Orach Chayim 632:1 follow this interpretation.

However, one should not sleep under the board. - According to the Maggid Mishneh, because it is part of the wall; according to the Kessef Mishneh, because it appears to be a separate domain.

A person who did sleep - or fulfilled any other of the activities which must be performed in the sukkah

under the board has not fulfilled his obligation.

There were boards that were four handbreadths wide, but less than four handbreadths thick. A person turned them on their side so that they would not be four handbreadths wide to use them as s'chach. This is not acceptable, because a board is unacceptable for use as s'chach whether one uses its width or thickness. - Sukkah 14b explains that after the Sages forbade the use of such boards, they are considered to be equivalent to iron poles.

The Magen Avraham 629:22 writes that at present it is customary not to use boards as s'chach, even if they are less than four handbreadths wide. However, if there is no other s'chach available, one may use boards for that purpose even if they are more than four handbreadths wide.

A roof which is not covered by a ceiling - i.e., the plaster and the stones - but rather has only boards fixed in place, is not acceptable, since they were not placed there for the purpose of a sukkah - as required by the following halachah

but to be part of the house. Therefore, if one - performed two activities:

a) lifted up the boards - from their place. (Though the Shulchan Aruch, Orach Chayim 631:9 does not mention this requirement, the Mishnah Berurah 631:4 does.)

and b) removed the nails - holding the boards in position. (See the Rambam's commentary on the Mishnah, Sukkah 1:7.) Through these actions, one is considered to have nullified the previous placement of the boards, and it is considered as though they have been placed there...

with the intent [that they serve] as a sukkah - Therefore

it is kosher - for the boards are essentially fit to be used as s'chach. The only difficulty was the intention with which they were originally placed. A change of mind without an act is not sufficient, since, as explained in the commentary on the following halachah, we are required to "make" a sukkah and not use one which has already been made.

[This applies provided] that each board is not four handbreadths wide. - as explained in the previous halachah. Rabbenu Asher states that in such a situation, the sukkah is acceptable even though the boards are more than four handbreadths wide.

He explains that in the previous instance, the reason the Sages forbade using such boards was to differentiate between them and the boards of a house. In the present instance, the fact that the person took apart the roof of his house obviously implies that he realizes that it may not be used as a sukkah. Hence, there is no need for such a decree. This opinion is accepted by the Shulchan Aruch, ibid.

A sukkah that was made for any purpose whatsoever - even if it was not made for the purpose of [fulfilling] the mitzvah - if it was made according to law - Sukkah 8b quotes a baraita which contains the latter statement and questions: "What does 'according to law' mean?...That it was made for the purpose of shade."

It appears that the Rambam uses the same expression, but with different implications. Since he explicitly states that the sukkah must be constructed for the purpose of shade, one might infer that the expression "according to law" is intended to include other concepts. Thus, it can be a reference to the requirements for a sukkah's size and the nature of the materials used for the s'chach, as mentioned in this and the previous chapter.

it is kosher. - The Mishnah, Sukkah 1:1, states:

An old sukkah: The School of Shammai deems it unacceptable, while the School of Hillel rules it kosher.

The commentaries explain that the term "an old sukkah" refers to any sukkah that was constructed for purposes other than the fulfillment of the mitzvah.

In its discussion of this law, the Jerusalem Talmud requires that one must make an addition or change to the s'chach. Though that decision is not quoted by the Rambam, Rabbenu Asher mentions it and it is accepted by the Shulchan Aruch (Orach Chayim 636:1). Nevertheless, the Magen Avraham 636:1 explains that this is a desirable and proper step, but the sukkah is acceptable even though no changes have been made.

However, it must be made for the purpose of shade. - Isaiah 4:6 states: "It shall be a sukkah for shade from the heat...," thus defining the purpose of such a structure. A sukkah constructed for the purposes of modesty is not acceptable (Rabbenu Manoach).

Examples of this are sukkot made for gentiles, sukkot made for animals, and the like - which are outside the entire framework of mitzvot. Sukkah 8b also mentions the sukkot made for shepherds and watchmen. Though the latter are obligated to keep the mitzvah of sukkah, they did not necessarily construct their sukkot with that intent in mind.

In contrast, a sukkah that came about on its own accord - e.g., branches fell over a frame, and of course, any time a roof is covered for other purposes - e.g., the construction of a home, as mentioned in the previous halachah...

is unacceptable, because it was not made for the purpose of shade.

Similarly, when a person hollows out a place in a heap of produce and thus makes a sukkah, it is not considered to be a sukkah - Sukkot 12a explains that there is an added factor involved in this example. Deuteronomy 16:13 states: "Make a [celebration of] the Sukkot holiday for seven days." This refers to the construction of the sukkah and teaches that we must "make" a sukkah and not use what was already made. Therefore, despite the fact that the person hollowed out the space for the purpose of shade, the sukkah is not acceptable, because the produce was not originally placed there for that purpose.

We find a similar principle concerning tzitzit. Deuteronomy 22:12 states: "Make yourself tassels on the four corners of your garments." On the basis of this command, Menachot 40b teaches that it is unacceptable to tie tzitzit to a three-cornered garment and then cut a fourth corner, since we are required to make tzitzit, and not use what is already made.

for the produce was not piled there for this purpose. - The Ba'al Hamaor writes that if, originally, a person were to pile produce with the intention that later he would hollow out a sukkah, the sukkah would be acceptable. However, this opinion is not accepted by other authorities.

Accordingly, were one to create a space one handbreadth [high] - We find the measure of one handbreadth considered to define a structure with regard to the laws of ritual impurity. Accordingly, it is given significance in this context as well. (See Sukkah 16a.)

and seven [handbreadths] - by seven handbreadths

in area for the purpose of a sukkah, and afterwards hollow it out till it reached ten [handbreadths] - the minimum height of a sukkah, as explained in Chapter 3, Halachah 1.

it is kosher, since its s'chach was placed for the purpose of shade - and then, the original structure was merely expanded.

We may not use bundles of straw, bundles of wood or bundles of reeds as s'chach. - Although, according to the Torah's requirements, these would be considered proper s'chach...

This decree [was instituted] - by the Sages (Sukkah 12a)...

lest one place those bundles on one's roof to dry out, and then change one's mind and sit under them with the intent [that they serve as] a sukkah. The person did not place the s'chach there originally for the purpose of shade. Thus, it resembles a sukkah that came about on its own accord. - which is unacceptable, as explained in the previous halachah.

If one - placed bundles of these substances on a roof with the intent that they would be used as s'chach and...

untied [the bundles], they are acceptable [for use as s'chach]. - The Shulchan Aruch (Orach Chayim 629:17) explains that a different rule applies if the bundles were originally placed on the roof to dry out. For them to be acceptable as s'chach, untying them alone is insufficient, and one must also shift the position of their contents.

A bundle is considered to be no fewer than twenty five units. - Thus, any lesser amount of these substances are acceptable as s'chach even though they are tied together.

The Rambam bases his statements on the Jerusalem Talmud (Sukkah 1:6). Though the Ra'avad maintains that a bundle may be composed of even a smaller number of units, the Rambam's opinion is accepted as halachah by the Shulchan Aruch (Orach Chayim 629:15.

Though the Sages instituted the decree mentioned in the previous halachah, they made certain exceptions. Therefore...

Small bundles - The Kessef Mishneh questions the reason for the addition of the adjective, noting that if the bundles contain fewer than twenty five units, they are permitted, as stated in the previous halachah. Others mention that this refers to bundles of small branches.

that were tied together [to be sold] by number - to be untied immediately thereafter (Shulchan Aruch, Orach Chayim 629:16).

may be used as s'chach. - Sukkah 13b relates that bundles of this nature were frequently used in Sura, and that the Sages permitted them to be used as s'chach.

Similarly, if one cuts off the top of a date palm and the branches are bound to it, it may be used as s'chach, because elements that are bound naturally are not considered to be bundles. - The Ba'al Hamaor questions whether this principle applies only with regard to s'chach, where it is logical to assume that a more lenient position would be taken, since the entire question revolves around a Rabbinic decree, or whether it also applies in all cases where Torah law itself requires a bundle.

Furthermore, even if one tied the tops of the branches from one side and they thus appear to be a single bundle with one of its two ends bound naturally and the other bound as a result of human activity, it may be used as s'chach. A tree which is bound up is not considered to be a bundle, but rather a single piece of wood, since [the branches] are bound together naturally. - However, if one were to add even one branch and then tie them together, it would be considered to be a bundle (Shulchan Aruch, Orach Chayim 629:15).

Similarly, any knot which is not strong enough to hold when carried is not considered a knot [and the resulting bundle may be used as s'chach]. - Sukkah 13b mentions this principle when explaining why bundles of willows whose upper tie was loosened could be used as s'chach.

A person who constructs his sukkah under a tree is considered as though he built it within his home - and the sukkah is unacceptable. This applies only when the shade the tree produces exceeds the open area. However, if there is more open space under the tree than shade, the sukkah may be kosher.

The determination of whether such a sukkah is kosher depends on a number of principles, based on the interpretation of Sukkah 9b and 11a. The Rambam's interpretation of that passage, and thus the ground rules he establishes, differ from those accepted by the Shulchan Aruch (Orach Chayim 626:1-2).

In the following halachah, the Rambam deals with the resolution of the question when no effort has been made to correct the problem of the non-kosher s'chach. As will be explained, there his interpretation is contested by other authorities. In this halachah, the Rambam describes the rulings which govern the situation when an effort has been made to rectify the situation by detaching the branches from their source of nurture. These are based on the Mishnah, Sukkah 11a, and are also accepted by other Rabbinic authorities. (See the Shulchan Aruch, Orach Chayim 626:2.)

If one draped the leaves and branches of trees [over the sukkah], and then placed s'chach over them, and only afterwards detached them - As mentioned in Halachot 1 and 2, branches are fit to be used for s'chach only after they have been detached from their source of nurture.

[the following rules apply:]

If the amount of [kosher] s'chach exceeded [the branches], it is kosher. - Though at present, the branches would be acceptable as s'chach, as explained in the commentary on Halachah 9, the Torah requires that when s'chach is originally put in place, it must be kosher. Otherwise, it is unacceptable even though steps were taken to correct the disqualifying factors. This is based on the principle that one must make a sukkah and not use one which is already made.

Nevertheless, since the prohibition against using these branches as s'chach does not relate to their essential nature, their presence may be nullified when there is a majority of kosher s'chach. This conforms to the principle of ביטול ברב.

If the amount of s'chach which originally was kosher did not exceed [the branches] - the presence of the branches remains halachically significant. Hence,...

one must move them - i.e., each of the branches individually (Shulchan Aruch, ibid.)

after detaching them, so that they will have been put in place for the purpose of a sukkah. - Moving the branches negates their previous placement, and afterwards they are considered to be kosher s'chach, which was put in place for the purpose of creating a sukkah.

If one mixed a substance which may be used for s'chach with a substance that may not be used for s'chach - This may refer to a substance like metal, which is unfit for use as s'chach because it does not grow in the earth, or branches of a tree which have not been detached from their source of nurture.

and used - the mixture of...

the two as s'chach, even though the quantity of kosher s'chach exceeds that of the substance which was not acceptable as s'chach - The presence of the substance which is not acceptable as s'chach is not nullified according to the principles of ברב ביטול, because it exists as a separate entity which can be distinguished from the kosher s'chach.

Rav Avraham, the Rambam's son, notes the apparent contradiction between this decision and Halachah 3, which states:

[When one uses] branches from a fig tree which contain figs,...We see if the waste is more than the food; then we may use them as s'chach.

That halachah also mentions kosher s'chach - the branches - and substances which are not acceptable as s'chach - the figs. However, if there is a greater quantity of branches, the presence of the figs is nullified. In contrast, in this halachah, that concept is not applied.

Rav Avraham distinguishes between the two. In Halachah 3, the person does not intend to use the fruit for the purpose of shade; he merely wants to save the effort of removing it from the branches. Therefore, their presence may be nullified. In contrast, in this halachah the substances which are not acceptable as s'chach are being employed for the purpose of shade itself. Hence, their presence cannot be nullified.

[the mixture] is not acceptable. - As mentioned above, this decision depends on the Rambam's interpretation of Sukkah 9b. That passage reads:

A person who constructs his sukkah under a tree is considered as though he built it within his home...

Ravva said: "The above applies only to a tree whose shade is greater than its open space. However, if its open space is greater than its shade, it is kosher.

What difference does it make if its open space is greater than its shade, the substance not acceptable as s'chach will be combined with the kosher s'chach [and therefore, the sukkah will not be acceptable]?

Rav Pappa said: בשחבטן.

The Maggid Mishneh, the Ra'avad, and Rabbenu Manoach explain that the Rambam renders בשחבטן as "when he separated them." Thus, when the two substances were combined, the Rambam's opinion would be that the sukkah is not kosher, as explained in this clause of the halachah. When they are separate, the sukkah may be kosher according to the stipulations mentioned in the following clause of this halachah and the halachot to come.

(The Kessef Mishneh explains that the Rambam renders בשחבטן as "when he severed them." However, that difference in interpretation does not result in a difference in halachah.)

Rashi and others interpret בשחבטן as "when he lowered them (and mixed them together with the kosher s'chach)." Thus, according to this opinion, the sukkah is acceptable when the kosher and non-kosher s'chach are mixed together. Thus, this view is diametrically opposed to the Rambam's, who maintains that such a mixture is of no avail.

As noted by the Shulchan Aruch (Orach Chayim 626:1), there are two ways of understanding this interpretation of the passage. However, since both of them are not acceptable to the Rambam, their explanation will not be included here.

If one covered the sukkah with the two substances and kept them separate - When there is a majority of kosher s'chach, it is judged to be an independent entity. When there is a sufficient amount of kosher s'chach, the sukkah is kosher unless the substance that is not acceptable as s'chach is placed in a manner which can disqualify the entire sukkah, as is explained in this and the following three halachot.

[the following rules apply:] If there are more than three handbreadths of the substance which is not acceptable as s'chach in one place - The principle of l'vud, by which this substance could be considered to be a continuation of the kosher s'chach, cannot apply. However, if there is less than three handbreadths of the substance that is not acceptable as s'chach in one place, even though there are a number of such patches among the s'chach, the sukkah is kosher, as stated in Halachah 16. Furthermore, one may eat and sleep under the non-kosher s'chach (Shulchan Aruch, Orach Chayim 632:1).

whether - the substance which is not acceptable as s'chach is placed...

in the middle of the sukkah or at its side, it is not acceptable. - As stated in the following halachot, this is relevant only with regard to a sukkah which possesses the minimum area. The reason the sukkah is not acceptable is not that it is disqualified by the non-kosher s'chach, but that it does not have the minimum amount of kosher s'chach (Sukkah 17b).