Shabbat - Chapter 16

This is the laws pertaining to a karpef, a large area that is enclosed by four walls, but these walls were not constructed for the purpose of habitation. Since this area is enclosed by four walls, it is considered a private domain according to Torah law. Nevertheless, as the Rambam continues, the Rabbis imposed certain restrictions on carrying within this space for the reasons mentioned below. We are, however, allowed to carry within an area enclosed for the purpose of habitation regardless of how large it is (Rambam's Commentary on the Mishnah, Eruvin 2:5).

The size of this space is defined in Halachah 3.

Since this is a large space in which there are no inhabitants, it appears to resemble a public domain or a carmelit. Accordingly, the Sages placed certain restrictions on carrying within it, lest one err and carry in the public domain as well (Shulchan Aruch HaRav 358:1).

A surface four handbreadths by four handbreadths that is elevated ten handbreadths above the ground is considered to be a private domain.

I.e., although it is a private domain according to Torah law, our Sages forbade carrying upon it for the reasons explained in the previous halachah.

Although one is allowed to carry from one carmelit to another, one may not carry more than a total of four cubits.

If it is less than four handbreadths by four handbreadths, it is a makom patur, and there is no difficulty in carrying from it to the sea or from the sea to it.

A rock that is this high above the sea and this size is considered to be a private domain.

Although our Sages generally forbade transferring an article from a private domain to a carmelit, since this is a very unusual circumstance they did not include it in their decree.

Eruvin 23b identifies the area in which two seah o [grain can be sown with the courtyard of the Sanctuary in the desert, which was 100 cubits by 50 cubits.
The Shulchan Aruch HaRav explains the significance of this concept. All of the prohibitions against labor on the Sabbath are derived from the Sanctuary. The courtyard of the Sanctuary was a large area which was enclosed for purposes other than habitation. Nevertheless, it was permitted to carry within it. Therefore, when the Sages prohibited carrying in large areas that were enclosed for purposes other than habitation, they used the size of the courtyard of the Sanctuary as the lower limit.

Here we see a contrast to the measures offour handbreadths by four handbreadths or four cubits by four cubits, where the intent is a square or a larger area in which such a square could be inscribed.

In his Commentary on the Mishnah (Eruvin 2:5), the Rambam states that the square is approximately 70 cubits and five sevenths of a cubit by 70 cubits and five sevenths of a cubit, but that there is no perfect square root for the number 5000.

This is obvious from the connection to the courtyard of the Sanctuary, which, as mentioned, was a rectangle and not a square.

Note the Rambam›s explanation of the difference in opinion between Rabbi Yosse and Rabbi Eliezer, in his Commentary on the Mishnah (Eruvin 2:5). On the basis of this explanation, it would appear that his conception of the Mishnah is closer to that of Tosafot, Eruvin 23b than to that of Rashi (loc. cit.).

As in a carmelit.

Hence, when such an open area does not resemble the courtyard of the Sanctuary, the leniency does not apply.

Once this extent of a wall has been broken down, it is considered as if the entire wall is no longer of significance as indicated in Halachah 16.

When one re-encloses the wall, it is considered as if the entire enclosure has been made for the purpose of habitation. Therefore, the area is considered to be an ordinary private domain, and one is allowed to carry within without restriction.
The Maggid Mishneh questions the Rambam’s statements on the basis of those of Rashi, Eruvin 24a, which state that the intent to use the enclosure for habitation is not sufficient. There must be a house that opens up to the enclosure.
The Merkevet HaMishneh states that, according to the Rambam, “habitation” does not necessarily mean “human habitation.” Therefore, the intent could be to use the enclosure as a corral for animals or the like. Rav Kapach cites the Rambam’s Commentary on the Mishnah (Eruvin 2:5), from which it appears that as long as there is a storage vat in the enclosure, it is considered as “enclosed for the purpose of habitation,” although it does not contain a house or lead to a house.
Thus according to the Rambam, “everything depends on the person’s intention.” If he encloses the area for the sake of habitation, he is allowed to carry freely within it. Why is this leniency granted? Because the prohibition against carrying within such an area is Rabbinic in origin, and the Sages enforced this stringency only when a person’s intent was not for the sake of habitation, for then the enclosure resembles a public domain. The Shulchan Aruch (Orach Chayim 358:2), however, follows Rashi’s view, that a house is required within the enclosure or the enclosure must lead to a home.

Since the entire enclosure was never opened up for ten cubits at one time, one might assume that the original enclosure was never nullified. Nevertheless, since ultimately a span of ten cubits was constructed, the enclosure is considered as םינפ, תושדח “a new entity” (Shulchan Aruch HaRav 358:8). Note a parallel ruling in Hilchot Kellim 6:2.

A mil is approximately a kilometer in contemporary measure.

Although the area was enclosed for the purpose of habitation originally, since it is large and the person sowed produce within the majority of its space, it is clear that he considers it to be a commercial field or garden. lt is not common for people to dwell in such a place (Rashi, Eruvin 23b).

I.e., one may carry only within a square of four cubits even in the portion of the enclosure where the produce was not sown, because there is no barrier enclosing the area on the side that faces the portion where the produce has been sown (Maggid Mishneh). Alternatively, the portion in which the produce was not sown is considered to be a secondary part of the entire field in which it is forbidden to carry (Rashi, Eruvin 24a).

Obviously, if produce was sown in a smaller portion of the enclosure, the same leniency applies. The portion of a field necessary to sow two seah of grain is the upper limit.

In such an instance, the portion of the enclosure in which produce was sown is considered like a private garden a person has in his yard.

Since the produce was planted in such a large area, it is considered like a commercial garden or field.

In this instance, the commentaries quote the opinion of the Maggid Mishneh mentioned above: that the portion of the enclosure facing the side where the produce has been sown is not considered to be enclosed.
The Turei Zahav 358:6 is more lenient and explains that since according to the Torah, one could carry within the entire enclosure, even according to Rabbinic law one should be allowed to carry within the portion where produce was not sown. His opinion is not, however, accepted by the later authorities.

The Mishnah Berurah 358:63 states that this ruling applies even when one planted trees throughout the entire enclosure.

It is a common practice to plant trees in one’s yard for shade. Hence, planting them is not considered to be a sign that one rio longer considers the enclosure to be intended for the purpose of habitation.

The Rashba states that this applies when the water is ten handbreadths or more deep. If it is shallower than that, there are no restrictions on carrying within the enclosure. Although Sefer HaBatim differs with this interpretation, the Rashba’s ruling is accepted by the Shulchan Aruch (Orach Chayim 358:11).

Rashi (Eruvin, loc. cit.) states that the water must be fit to drink. The Rashba and other Sephardic authorities state that it is sufficient that the water be fit for laundry and the like. This appears to be the Rambam’s view. Although the Shulchan Aruch (loc. cit.) quotes Rashi’s view, Sha’ar HaTziyun 358:81 states that one may rely on the Rashba’s ruling.

For, indeed, it is an advantage to have a source of water near one’s home. Hence, the water does not nullify the enclosure (Rashi, loc. cit.).

From the gloss of the Magen Avraham 358:15, it appears that if the area in which the water is collected is set off from the enclosure as a whole because its height descends abruptly, we may carry within the remainder of the enclosure.

The Maggid Mishneh explains that according to the Rambam’s interpretation of Eruvin 25a, this refers to a roof that is open on all sides, which the watchmen in a garden construct for shade. The Rashba interprets that passage as referring to a roof with two proper walls that are joined at one corner. Rabbenu Chanan’el’s interpretation of that passage also indicates that the sides of the covered area are entirely open.

Note the Kessef Mishneh and the Shulchan Aruch (Orach Chayim 358:12), where Rabbi Yosef Karo states that this principle applies even when the roof is sloped. Generally, the principle, “The edge of the roof is considered to descend and close off,” does not apply with regard to a sloped roof. Nevertheless, since according to the Torah itself, it is permitted to carry within this enclosure, leniency is allowed. (Compare also to Chapter 17, Halachah 35.)
lt must be emphasized that according to the Maggid Mishneh’s understanding of the Rambam’s rulings (see note 33), this entire matter is extraneous.

Thus, the remainder of the enclosure is not larger than the space necessary to sow two seah of grain. Hence, there are no restrictions against carrying within it.

This represents the Rambam’s interpretation of a passage in Eruvin 25b. Although Rabbenu Chanan’el and Rav Zerachiah HaLevi interpret the passage in this manner, the Ra’avad, Rashi, the Rashba and others follow a slightly different version of the text, and therefore interpret the passage differently. Their interpretation is quoted in the Shulchan Aruch (Orach Chayim 358:13).

According to the (and seemingly, also according to Rabbenu Chanan’el), both openings are no more than ten cubits wide. Otherwise, it would be forbidden to carry within the courtyard.

The Maggid Mishneh explains that the Rambam is referring to a T-shaped area in which the enclosure opens up to the courtyard, which extends on either side. The enclosure is not considered part of the courtyard, nor is the courtyard considered part of the enclosure, and the laws that originally applied to both areas continue to apply.

I.e., we do not say that the enclosure becomes considered as an extension of the courtyard.

So that one will be able to carry within it.

Since it is common to plant trees in such enclosures, even when the trees are ten handbreadths high and four handbreadths by four handbreadths in area (at which point they are considered to be a separate domain in certain contexts), they do not reduce the size of the enclosure (Maggid Mishneh in the name of the Rashba).

Rashi interprets Eruvin 25a, the source for this halachah, as referring to a pillar of this size, whether it is in the middle of the enclosure or next to the wall. Rashi’s interpretation is followed by the Shulchan Aruch (Orach Chayim 358:5).

Thus, if the area of the enclosure minus the area of the pillar is less than 5000 square cubits, one is allowed to carry within it.

Based on the principle of l'vud, the pillar is not considered to be an independent entity, but rather an extension of the wall. Therefore, although in practice, the open space within the enclosure has been reduced in size, this reduction is not considered as halachically significant.

1. e., the size of the enclosure is calculated from the new partitions. If it is less than 5000 square cubits, one may carry within. lt must be noted that, with regard to this clause as well, Rashi interprets the Talmudic passage differently, explaining that the new partition is erected to enclose the area for the purpose of habitation. His interpretation is accepted by the Shulchan Aruch (loc. cit. :6).

Because of the principle of l’vud.
The Maggid Mishneh questions this ruling on the basis of the first clause of the following halachah, which states, “If one applies cement to the wall, one reduces [the size of the enclosure].” Since the cement reduces the size of the enclosure, even though it actually becomes part of the wall, one could surely assume that a new partition would reduce the size of the wall although it is considered part of the wall because of the principle of l’vud.
The Maggid Mishneh explains that since the partition is halachically insignificant, it cannot take the place of the previous wall. Hence, it is not considered to reduce the size of the enclosure. ln contrast, the cement adds on to the size of the previous wall, and the space it takes up is subtracted from the open space of the enclosure.

I.e., if the entire space taken up by the cement that is added to the wall is sufficient to reduce the size of the enclosure to less than 5000 square cubits, one may carry within the enclosure.

In this instance as well, the Ra’avad differs with the Rambam. Based on his interpretation of Eruvin 25a, the cement is counted only when it is substantial enough to stand on it is own if the original wall was removed. Although the Shulchan Aruch (Orach Chayim 358:7) follows the Ra’avad’s view, the Mishnah Berurah 358:55 states that the Rambam’s opinion may be relied upon in time of need.

We are speaking about a mound ten handbreadths high which is considered as set apart as a separate domain. Since the area is being surrounded by a partition that is constructed for the purpose of dwelling, one might think that it would be permissible to carry within the enclosure. Nevertheless, this is forbidden for the reason stated by the Rambam.

Since the mound, the original dividing point for the enclosure, is still standing, the new walls built are not considered significant.

As mentioned in the previous clause, as long as the original wall is visible, the new wall is of no consequence.

And less than ten handbreadths of the original wall extends above the ground (Mishneh Berurah 358:57).

Our translation is based on the Mishnah Berurah 359:1, which states that in Talmudic times there would be yards both in front and behind the homes. A yard in front of a home was referred to as a. רצח These were frequently used by the people of that era and mentioned often in the Talmud. A yard behind a home was referred to as a, הבחר a term used comparatively rarely in the Talmud. These yards were used infrequently by people of that era.

As apparent from the following clause, this applies when the yard was enclosed before an entrance leading to one of the homes was opened.
The Ramah (Orach Chayim 359:1) rules that the restriction mentioned in this law does not apply at present, since it has become customary to use our back yards. Hence, we assume that they were enclosed for the purpose of habitation.

Eruvin 24a states that this leniency applies even when a portion of the yard is used as a threshing floor. Since the person enclosed the area after opening an entrance to his home, we assume that the yard’s primary purpose is to serve the home.

The yard is larger than 5000 square meters and was enclosed for purposes other than habitation (Rashi, Eruvin 24b).

The Rambam›s decision is based on the description of such a yard in Eruvin 24b.

Using a post, a lechi, as a divider is discussed in Chapter 17, Halachot 2 and 9.
As the Rambam mentions there, the post is considered as a fourth wall. In this instance, by erecting the post, one will be considered as erecting a new wall to enclose the yard for the sake of habitation (Rashi, loc. cit.).

This refers to a city surrounded by a wall, which is considered to be a private domain.

This refers even to an inferior partition, such as those mentioned in Halachah 18. Rashi (Eruvin 16b, the source for this› halachah) states that the restrictions of this law apply only when the enclosure uses such an inferior partition. If a proper partition is erected, one may carry within the entire enclosure, since the enclosure was erected for the purpose of habitation. Note the Merkevet HaMishneh, who emphasizes that the Rambam does not accept this leniency.
The wording of the Shulchan Aruch and the Beit Yosef(Orach Chayim 360:1) appears to concur with Rashi›s view. The later authorities also accept his ruling.

Since the area is so large and it is enclosed only for a temporary period, the Sages placed restrictions on carrying within it.
lt must, however, be emphasized that according to Torah law, the enclosure is considered a private domain. Accordingly, a person who carries from it to a public domain or from a public domain to it is liable (Shulchan Aruch HaRav 360:1; Mishnah Berurah 360:5).

With this term, the Rambam excludes a gentile. The Ramah (loc. cit.) also rules that a gentile may not be included in a caravan.

According to Torah law, such an area is a private domain. The Rabbis did not place any restrictions upon it, because it has—albeit temporarily—been enclosed for the purpose of habitation.

See Shulchan Aruch HaRav 360:2, which mentions that it is acceptable if the land is used for pasture.

Since the enclosure includes such a large empty space, our Sages forbade carrying within it.

The Jerusalem Talmud (Eruvin 1:10) does not resolve the question whether or not to count a child as a member of the caravan. In his Beit Yosef (loc. cit.), Rav Yosef Karo questions the Rambam’s decision, for generally we follow the rule that when a doubt exists pertaining to a question of Rabbinic law, the more lenient view should be followed. Accordingly, he does not mention the matter in his Shulchan Aruch. The Ramah cites the Rambam’s view, but prefaces it with the phrase “There are those who maintain,” which implies that the opinion cited is not accepted universally.

I.e., greater than 5000 square cubits.

This leniency applies only on the Sabbath on which the person dies. On the following Sabbath, they are forbidden to carry unless they are joined by a third individual.

See a further expression of this principle in Hilchot Eruvin 3:25.

I.e., the middle enclosure does not have a wall, but is totally open on either side (Shulchan Aruch, Orach Chayim 360:3). The Shulchan Aruch, however, follows the interpretation of the Ritba, who requires the walls of the narrow courtyard to enter into the space of the wider courtyard. The Rambam, however, does not appear to make such a requirement.

Since the individuals in each of the outer courtyards are considered as sharing the space of the middle courtyard.

I.e., they may carry freely from one enclosure to another. Note the Shulchan Aruch (loc. cit.), which states that they must make an eruv to join their respective enclosures together. Similarly, the Shulchan Aruch mentions a more restrictive opinion, which allows the individuals to carry freely only when the outer enclosures are less than 5000 square cubits in size.

I.e., the outer enclosures are considered to be distinct entities without any connection to each other. Thus it is not considered as if three people are spending the Sabbath in the same place.

The bracketed additions are based on the commentary of Rashi (Eruvin 93a, the source for this halachah) and the Shulchan Aruch (loc. cit.).

In both of these instances, three individuals share a single portion of space. Therefore, they are allowed to carry freely from one enclosure to another.

In this halachah, the Rambam begins to describe the rules that govern the walls that enclose a private domain.

I.e., it is as if the partition were not there. See notes below.
Rashi, Sukkah 24b, states that this applies not only when the wall will fall because of the wind, but also to a cloth wall that will blow back and forth. From Halachah 24, it appears that this ruling is also accepted by the Rambam. lt is quoted by the Shulchan Aruch (Orach Chayim 362:1 and 630:10).

Our translation follows Rabbenu Chanan’el’s text of Eruvin 26a. According to this interpretation, our Sages are teaching us that a partition must be constructed in a firm and sturdy fashion. (See also the interpretation of the term in the Aruch.) See also Halachah 12 and notes.
The Ra’avad, Rashi, and others follow a different text of the Talmud, which reads לכ. חציחמ חיושעח תחנל According to this interpretation, this refers to a partition erected for storage purposes and not for people to dwell within. This latter view is quoted by the Shulchan Aruch (Orach Chayim 362:1).

The commentaries on Eruvin interpret this as a temporary partition that builders construct for shade. (Rav Kapach, however, cites interpretations of the Geonim that interpret the term "for the sake of modesty" literally, to change one's clothes behind.)

The Maggid Mishneh interprets the phrase “it is not a complete partition” to mean: It is not a partition significant enough to cause an enclosure to be considered to be a private domain. It may, however, cause an enclosure to be considered to be a carmelit.

Our translation is based on the gloss of the Maggid Mishneh, which is quoted by the Shulchan Aruch (Orach Chayim 362:2).
See also the interpretation of Rabbenu Chanan’el to Eruvin 93b, which interprets it as a “rock.” From a halachic perspective, these interpretations are not mutually exclusive. See Chapter 15, Halachah 9.

1. e., if a wall includes open spaces, the area that is open may not exceed the area that is enclosed. As mentioned in the following halachah, this refers to open spaces that are larger than three handbreadths wide. As the Rambam states in Halachah 18, this refers to spaces in the horizontal as well as the vertical portion of the wall.

I.e., when there is an open space larger than ten cubits wide, the entire partition is nullified.

As long as the opening is ten cubits wide or less, there is no need to enclose it with a frame of an entrance. lt is commonplace for a wall to have an entrance that is less than ten cubits wide without a frame.

The Rambam explains the structure of a frame of an entrance (tzurat hapetach) in Halachah 19.

I.e., by erecting the frame of an entrance, one enables a partition to be considered acceptable despite the fact that it has an opening that is larger than ten cubits.

This ruling represents a point of difference between the Rambam and most other authorities. According to the Rambam, although the frame of an entrance enables an opening larger than ten cubits to be accepted, the opening is still considered an open space. Accordingly, if the total amount of open space on any one side of a partition exceeds the closed space, the partition is unacceptable, even though portions of the open space possess a frame of an entrance.
Many authorities (e.g., the Rashba and Tosafot, Eruvin lla) differ and maintain that once a frame of an entrance is constructed, the space below it is deemed closed and should be considered as such when calculating whether the enclosed portion of a partition exceeds its open area. The opinion of these authorities is accepted by the Shulchan Aruch (Orach Chayim 362:10). Nevertheless, Shulchan Aruch HaRav 362:19 and the Mishnah Berurah 362:59 state that it is proper to be stringent and follow the Rambam’s ruling.
Rabbenu Asher cites the Jerusalem Talmud (Eruvin 1:9) and Kilayim 4:2 as the source for the Rambam’s ruling. (See also Hilchot Shofar V’Sukkah V’Lulav 4:12, where the Rambam accepts a more lenient view regarding the walls of a sukkah. Note also the glosses of the Kessef Mishneh and the Maggid Mishneh there.)
See also the commentary of Rav Kapach, who advances an interpretation of the Rambam’s statements here and in his Commentary on the Mishnah (Eruvin 1:8) that maintains that the Rambam follows the view advanced by the Rashba. Even those who reject this interpretation in most instances are forced to accept it with regard to the third side of an alley, as stated in Chapter 17, Halachah 3. (Note also Chapter 17, Halachah 27.)
The difference between the Rambam’s ruling and that of the other authorities is particularly relevant in contemporary communities that permit carrying because of an eruv. Most of these communities are enclosed, not by a proper wall, but by a series of “frames of an entrance” coristructed using telephone poles and the like. According to the Rambam, these enclosures are not acceptable. Indeed, this is one of the reasons why the carefully observant refrain from carrying in these communities.

More precisely, the same ruling applies if some of the spaces are wider than three handbreadths, as long as the size of the total of the open spaces wider than three handbreadths does not exceed the remainder of the partition.

As the Rambam continues, a partition of reeds will generally be constructed by implanting them upright in the ground, one near the other. As long as the reeds are not three handbreadths apart, the partition is acceptable even if there are no reeds that run horizontally.

Generally, a partition of ropes will be constructed by stretching them from one post to another. As long as the ropes are not three handbreadths apart, the partition is acceptable, even if there are no ropes that run vertically.

In the Introduction to his Commentary on the Mishnah, the Rambam defines the Hebrew term halachah l’ Mosheh miSinai as referring to laws that have no obvious source in the Written Torah, yet have been accepted throughout the centuries as an integral part of the Torah tradition.

As the Shulchan Aruch (Orach Chayim 362:11) emphasizes, the reed must be placed exactly above the two side posts. lt is not acceptable for it to be attached to their sides, for then it does not resemble the lintel of a doorway.

In his gloss on this halachah, Rabbi Akiva Eiger explains that this is acceptable because of the principle gud asik—i.e., the posts at the side are considered to be extended until they reach the crossbar. Based on this rationale, it follows that the two posts need not be of the same height. Even if one is higher than the other, they may still be considered as part of the same frame of an entrance. (Note also the application of this principle in Hilchot Sukkah 4:2.)

According to the Shulchan Aruch (loc. cit.), this refers to the posts on the side. The crossbar above need not be sturdy at all.

The Rambam›s decision is based on Eruvin 11b. His ruling, however, has aroused questions. The passage cited also mentions opinions that require the post to have a hinge for the door on at least one side. Although there are authorities who also accept the latter requirement, the Shulchan Aruch (loc. cit.) follows the Rambam›s view.

I.e., the circular portion of the arch is not counted in the calculation of the entrance’s height.

I.e., there is an opening of more than ten cubits at the corner where two walls would merge if they were continued. Even if one constructs a frame of an entrance at this opening, it is not acceptable.

Note Chapter 17, Halachah 35, which mentions another law based on this same principle.

See parallels in Chapter 17, Halachah 12, and Hilchot Sukkah 4:16.

Unlike the animals that the Rambam proceeds to mention, a human being need not be bound, as is obvious from Halachah 23.

If the animal is standing and there are three handbreadths between the animal’s body and the ground, that space must be filled with other substances (Shulchan Aruch HaRav 362:12).

Note that in Hilchot Sukkot (loc. cit.), the Rambam does not require that animals be bound when they serve as part of a wall. The Shulchan Aruch (Orach Chayim 630:11) states that the animals must be bound even when used for the purpose of a sukkah’s wall.

The Shulchan Aruch (Orach Chayim 362:3) explains this as referring to a structure that was not built with the intent of enclosing an area, but accomplished that purpose nonetheless.

I.e., in all instances, the partition is considered valid, and the enclosure is considered a private domain. Therefore, a person who transfers an article into this enclosure f זom the public domain is liable. Our Sages, however, placed certain restrictions on carrying within such an enclosure, as the Rambam continues to explain.

I.e., the person who constructed the partition did so without knowing that it was the Sabbath or without knowing that it is forbidden to build on the Sabbath (Mishnah Berurah 362:18).

According to the Chemed Mosheh, this refers to a situation in which one person had another construct an enclosure for the former to carry within on the Sabbath. Although the person who actually constructed the enclosure did not intend to violate the Sabbath laws, the person for whom he performed the labor desired that such a violation take place. Hence, that person is prohibited from carrying within. This explanation resolves the question raised by the Rashba that is quoted by the Maggid Mishneh.

As mentioned in the notes on Chapter 6, Halachah 23, when a Jew intentionally performs a forbidden labor on the Sabbath, it is forbidden for other Jews to benefit from that labor on that Sabbath itself. The person who performed the labor, by contrast, is never permitted to benefit from it. Thus, in this instance, he would be forbidden from ever carrying within this enclosure on the Sabbath. (See Or Sameach.)
Note the Shulchan Aruch (loc. cit.), which states that if a partition had been standing before the Sabbath, it was removed on the Sabbath and then reconstructed on the Sabbath, it is permitted to carry within the enclosure. This applies even if the partition was rebuilt intentionally on the Sabbath. The Mishnah Berurah 362:26, however, cites authorities that do not accept this leniency.

I.e., within three handbreadths of each other (ShulchanAruch, Orach Chayim 362:5). Note the Bayit Chadash (Orach Chayim 362) and the Be’ur Halachah 362, which question why the people may not be even further separated.

Although constructing a partition of this nature is not considered as building, it is still forbidden for the people who stand there to have in mind that their bodies serve as an enclosure, lest they come to treat the Sabbath prohibitions lightly (Mishnah Berurah 362:39).

The Rashba differs with this ruling and maintains that there is no difficulty if the person who desires to use the enclosure has the people stand there. According to his opinion, the only difficulty is when the people forming the partition have such an intent. The Shulchan Aruch (Orach Chayim 362:7) prefaces the quotation of the Rambam’s ruling with the words, “There is one who says,” which implies that it is not accepted by all. Similarly, the later authorities do not obligate compliance with this stringency.
Significantly, when discussing the use of human beings as part of the wall of a sukkah on the holiday, the Rambam (Hilchot Sukkah 4:16) states that the people serving as the wall may not know that their bodies are being used in that capacity, but the person sitting in the sukkah may have that intent.

Note the Ramah (Orach Chayim 362:7), who states that the leniency of using human beings to form an enclosure on the Sabbath should be employed only in a very extreme situation. He maintains that it is preferable to have a child bring in an article from the public domain without making an enclosure, rather than to have an adult carry the article in within an enclosure consisting of human beings. Although the later authorities raise questions regarding employing a child for this purpose, they accept the Ramah’s hesitation about using an enclosure of human bodies.

For this rule to apply, there must be a place four handbreadths by four handbreadths in area and ten handbreadths high beneath the tree. Otherwise, the space is considered as a carmelit (Shulchan Aruch HaRav 362:2; Mishnah Berurah 362:5).

See Halachah 15. (See also Hilchot Sukkah 4:5, where the Rambam mentions similar concepts with regard to using a tree as a wall for a sukkah.)

As mentioned at the beginning of the chapter, when an area was enclosed for purposes other than habitation, one may not carry within it, if it is larger than the space necessary to sow two se’ah of grain—i.e., 5000 square cubits.