Rambam - 3 Chapters a Day

This refers to an instance where one pours impure water into a mikveh. See Halachah 5.
Compare to Hilchot Ma’achalot Assurot 12:12 which states with regard to wine associated with idolatry that a column of wine being poured is considered as connected to the lower container. That, however, is a unique stringency resulting from the severity of the prohibition against benefitting from such wine.

We do not say that since the object into or onto which it is being poured is impure, the impurity flows up the entire column. Rather than considering the column as a single entity, each portion is considered as separate [see the Rambam’s Commentary to the Mishnah (Taharot 8:9)].

The liquids are considered as a primary derivative of impurity. They impart impurity to the container in which they are held.

Thus it is considered as if liquids from the bottom container mixed with those of the upper container and imparted impurity to them.

Nevertheless, as the Rambam explains in his Commentary to the Mishnah (Machshirin 5:10), when the liquid one is pouring is hot, even if the bottom one is hotter, the vapors from the bottom container do not have such an effect on the liquids being poured.

I.e., because vapor from a hot pot is considered as connected to a cold entity above it.

In which instance, they would contract impurity, as stated in Hilchot Sha’ar Avot HaTum’ah 8:1.

Even if none of the liquid that collected on her hand dripped back into the pot.

These refer to the names of places in Eretz Yisrael, as stated in the Rambam's Commentary to the Mishnah (Machshirin 5:9). In his notes to that mishnah, Rav Kapach cites Joshua 15:24, 55 which mentions two places referred to as Zif; hence, the use of the plural. The commentaries have noted that they have not found a place called Tzapachat.

If one touches the honey and then withdraws his hand, some of the honey will ascend with his hand and remain extended between his hand and the honey. See Nazir 50b.

I.e., their honey is very thick; hence, it is considered as a single entity and by touching one portion, one is considered to have touched the entire amount.

Halachot 1 and 2 above.

I.e., a container that is not susceptible to ritual impurity. If the container was susceptible to ritual impurity, there would be no question that the water being poured would be considered as impure. For even if the water being poured were considered as connected to the mikveh, it would still be considered as impure. For the container would have contracted impurity from the liquids. It would then continue to impart impurity to them, counteracting the influence of the mikveh.

Chapter 2, Halachot 21-22.

That would cause liquids poured on it to flow down quickly [the Rambam’s Commentary to the Mishnah (Taharot 8:9)].

It appears that the other liquids were collected to the extent that they can be perceived as an independent entity, not merely felt as moisture.

If the liquid collected at the bottom is impure.

If the liquid collected at the bottom is a mikveh.

Impure food does not impart impurity to other substances unless it is the size of an egg-sized portion. Now, the three pieces reach that size only when combined. Thus the question is: Are they considered as combined or not? If they were considered as combined, they would impart impurity to the liquids which would in turn impart impurity to the kneading trough [the Rambam's Commentary to the Mishnah (Taharot 8:8)].

This is speaking about pieces of dough [or other foods] that are next to each other, but not attached to each other. The water does not cause them to be considered as combined, because, as stated in the previous halachah, water on an incline is not considered as a single unit. Hence, the drop of water between the upper two pieces is considered a separate entity from the drop between the pieces.

That together would comprise an egg-sized portion.

For there is one drop of water between them. That drop of water is touching an egg-sized portion of impure food.

Not just moisture that could be felt, but a collection of water that was not flowing.

Thus if all the small pieces together comprise an egg-sized portion, they impart impurity. The Kessef Mishneh interprets the measure of mustard seeds as referring to the water. If there is a mustard seed’s amount of water on the kneading trough, the pieces are combined. Rabbenu Asher, Rav Ovadiah of Bartenura, and others (Taharot, op. cit.) interpret the term as referring to the pieces of food: Even if they are as small as a mustard seed, the liquid can combine them.

Hilchot Sha’ar Avot HaTumah 10:2-3.

Such a person is referred to as a t’vul yom. He is still ritually impure until nightfall. Nevertheless, since he has already immersed, the degree to which he imparts impurity is reduced, as stated in the following halachah.

Causes them to be considered impure, but not to impart impurity to others. This applies even to the liquids. Although generally, liquids are always considered as primary derivatives, an exception is made in this instance.

See the following chapter.

I.e., it merely stems from a Rabbinic decree. See Hilchot She’ar Avot HaTumah 8:10-11.

I.e., he has done everything required of him and the requirement for his purification will come inevitably. See Hilchot Pesulei HaMukdashim 18:14 which mentions another leniency which, according to the Rambam, applies with regard to a person who immersed during the day but did not wait until nightfall.

T’vul Yom 1:5 mentions other foods in this category as well. The Kessef Mishneh questions why the Rambam does not include them. The commentaries explain that in Chapter 1, the Rambam excluded these foods from all types of ritual impurity, because they are not considered as designated for human consumption.

Barley and spelt are often used for animal fodder. Hence, when they are not shelled, leniency is granted. Wheat, by contrast, is almost exclusively used for human consumption. Therefore the laws are more stringent. See also Chapter 5, Halachah 12, where a distinction is made with regard to the shell itself.

See Chapter 5.

See Chapter 6, Halachah 9.

See the following chapter.

See Hilchot Sha’ar Avot HaTum’ah, ch. 8, with regard to the impurity of hands. Although both a person who immersed that day and impure hands only disqualify terumah and do not empower it to impart impurity, there are certain differences between the two.

See Hilchot Sha’ar Avot HaTum’ah 10:5 which mentions another such stringency.

The term challah can refer to a loaf of bread. It also refers to a portion of dough that is separated from a larger dough and given to a priest. The laws regarding such a portion are the same as those applying to terumah. From the fact that the Rambam mentions this concept in his Commentary to the Mishnah in the mishnah from which this law is derived (T'vul Yom 1:1), one might infer that he interprets the term as referring to loaves made from such separated portions of dough.

The Rambam is speaking about a situation in which the loaves and breads-and similarly, the other foods mentioned later on—are terumah. As mentioned in the previous chapter, ordinary food is not rendered impure when touched by a person who immersed that day.

In his Commentary to the Mishnah (ibid.), the Rambam writes that if they are left attached, their form will be destroyed. This obviously is not the person’s intent.

And the sides of the bubble are touching food that is terumah.

For they are nothing but air.

Even impurities of Rabbinic origin, as explained at the conclusion of the previous chapter.

And thus impure.

Since he did not intend to separate them, they are considered as a single entity.

Since their surfaces have already hardened, they will certainly become attached. Thus inserting them into the oven at this stage indicates that the person desires that they remain attached (ibid.:2).

For oil never produces large bubbles (ibid.).

In all these instances, the bubbles contain substance and hence, they are considered as joined to the entities at their sides.

Because it is much thinner than the remainder of the loaf.

In his Commentary to the Mishnah (ibid.:3), the Rambam explains that this term means "exposed to excessive heat."

2 cm. according to Shiurei Torah, 2.4 cm according to Chazon Ish.

Since they are small, they are not considered as separate and distinct entities, but as part of the loaf.

For these are considered as distinct and separate entities and not as part of the loaf.

Thus if impurity touches the burnt portion, the remaining portion is still considered as pure.

The Rambam’s ruling is based on his version of the Tosefta (Uktzin 2:4). The · conclusion of that Tosefta is quoted above, Chapter 5, Halachah 22. See the comments of the Ra’avad and those of the Kessef Mishneh who explains that there is no difference of opinion between the Rambam and the Ra’avad on this issue.

I.e., it does not contract impurity and therefore become forbidden. Our translation is based on the Rambam’s Commentary to the Mishnah (T’vul Yom 2:5).

They are impure, but not the remainder of the meat or the congealed sauce. For that sauce is not considered as a liquid. Were it considered as such, it would contract impurity in its entirety and then impart it to the other pieces.

The wine is still considered as pure.

I.e., its white and yolk mixed together.

But not the vegetable.

The entire vegetable does not become impure, only that stalk. There is room to say that even that stalk should not become impure, for the egg is ordinary food and does not contract impurity when touched by a person who immersed that day. Nevertheless, since the portion he touched was directly on top of the vegetable, the Rabbis ruled stringently.

I.e., bubbled when cooked; thus there is air between the places touched by the person and the vegetable. Our translation is taken from the Rambam's Commentary to the Mishnah (T'vul Yom 3:2).

And even that vegetable is not considered to have contracted impurity.

The frying pan contained food that was terumah and the strand of the egg extended to it (ibid.:3).

Since the contents of the barrel would have flowed out had the person not place his finger there, our Sages considered it as if he touched all the contents.
The Kessef Mishneh notes that, in Hilchot Ma’achalot Assurot 12:10, the Rambam discusses a similar situation with regard to a gentile who plugs a barrel of wine with his finger. There, however, the Rambam rules that if the barrel is perforated from the side, the wine below the hole is permitted. The Kessef Mishneh states that our Sages were more stringent concerning the consideration of foods as joined with regard to impurity than with regard to wine touched by gentiles.

That were terumah.

I.e., if the entire liquid was 101 or more times the portion he touched, the amount of impure liquid is considered insignificant and the entire amount is pure. If the entire amount is less than that figure, the entire amount is considered as impure.

Hilchot Terumot 14:14.

Obviously, the person was careful not to touch the wine once it had been designated as terumah, for that would disqualify it.

From the wording of the Rambam here, it appears that we are speaking about a vat of wine that was not terumah. This represents a change in his approach from his Commentary to the Mishnah (T’vul Yom 2:6; the source of this halachah) which speaks about the entire vat becoming disqualified, indicating that he considered the mishnah to be speaking about an instance where the wine in the vat was also terumah (Tosafot Yom Tov, T’vul Yom, op. cit.).

The fact that he touched the other wine in the vat is not significant, for that wine is not terumah and will not be disqualified when touched by a person who immersed that day.

I.e., he held the jug from its sides or from the top of the rim without inserting his hand inside at all.

And the wine in the jug is not disqualified.

And is hence disqualified.

I.e., it was not a vat built into the ground, but an oversized tank (Kessef Mishneh who explains that there is no difference of opinion between the Rambam and the Ra’avad on this point).

A kor is 249 liter according to Shiurei Torah and 486 liter according to Chazon Ish.

For everything in the container is considered part of its contents and not a separate entity.

Even the wine at the top of the container.

Which is offered with the meal offerings and is part of the incense offering See Hilchot Issurei Mizbeach 6:8 where the Rambam states that although frankincense and the like are not foods — and hence would not ordinarily contract ritual impurity — because of the cherished nature of consecrated articles, it is possible for them to contract ritual impurity.

Even though every grain of these substances is a separate entity and thus the remainder is not joined to the portion touched by the person who immersed, because of the cherished nature of consecrated substances, our Sages were stringent and considered the entire amount as a single entity. In his Commentary to the Mishnah (Eduyot 8:1; see also Hilchot Sha’ar Avot HaTum’ah 12:7), the Rambam cites Chagigah 24a where this concept is derived from a non-literal interpretation of Numbers 7:14, “One golden ladle, [weighing] ten [shekalim], filled with incense.” Our Sages ruled that everything that is in the ladle is considered as one entity. Moreover, the Rambam follows the opinion of Rabbi Akiva in Eduyot, loc. cit. which maintains that even if the consecrated entities are located on a board, a tablet, or the like — i.e., an implement that does not have a cavity that serves as a container — they are all considered as joined.

And thus are treated as consecrated articles. See Hilchot Avodat Yom HaKippurim 2:5.

And this stringency is applied only because of the cherished nature of holy articles.

See Hilchot Temidim UMusafim 3:5.

Which ran through the Temple Courtyard.
The Ra’avad objects to the Rambam’s ruling, maintaining that as long as the coals are in the firepan, they are considered as consecrated and, hence, are susceptible to ritual impurity. The Kessel Mishneh justifies the Rambam’s ruling.

Since they are ordinary food, even if the person who had immersed had touched the stew or the cake, he would not have disqualified them.

Even though the oil permeates the entire vegetable, it is not considered as joined. Rabbenu Asher (T’vul Yom 3:5) explains that oil would cause terumah or consecrated food to be considered as joined, but does not have that effect on ordinary food.

In his Commentary to the Mishnah (T’vul Yom 2:3), the Rambam writes that it was common practice to crush garlic in oil and use it as a condiment for cooked foods.

Since the stew is terumah, it is considered to have joined everything together.

Since the stew is ordinary food, it does not join all the other elements together.

I.e., the entire mixture is considered as terumah [the Rambam’s Commentary to the Mishnah (op. cit.)]. Hence, if such a person touches any portion of the mixture, it is all disqualified.

I.e., he desires that the garlic be crushed into small pieces which are separate from each other. Therefore, it is not considered as a single entity the Rambam’s Commentary to the Mishnah (T’vul Yom 2:3)]

I.e., he deviates from the usual process and does not collect them while mixed with liquids. Were he to have collected them together with liquids, they would have been considered as joined (ibid.).

See Chapter 6. Halachah 14.

The portion of a dough given to a priest which is governed by the same laws as terumah.

Even the part that was not challah, nor directly adjacent to it.

Because it was once a totally distinct entity and even now, the intent is not that it become mixed into the remainder of the dough (for then, the entire dough would have to be eaten like terumah).

When ordinary food becomes mixed with terumah and the ordinary food does not constitute 101 times the terumah, the mixture is forbidden to a non-priest and must be eaten with the stringencies required for terumah. See Hilchot Ma’achalot Assurot, ch. 15; Hilchot Terumot, chs. 13-14, for more details concerning mixtures of terumah and ordinary food.

In which instance, the entire dough is considered as if it were mixed with terumah and is forbidden to be eaten by non-priests even if the yeast was one thousandth of the entire total (Hilchot Ma’achalot Assurot 16:2).

Although the terumah is significant with regard to the prohibitions regarding eating, it is not considered as significant with regard to impurity.

The bracketed additions are added on the basis of the Rambam’s Commentary to the Mishnah (T’vul Yom 3:4).

Since the dough was kneaded with fruit juice and not water, all of the different portions are not considered as connected to each other. See Chapter 6, Halachah 13.

I.e., the person himself is pure, but his hands are impure due to Rabbinic decree, as mentioned in Hilchot She’ar Avot HaTum’ah 8:8.

A portion which the Levites must separate from the tithe and give to a priest. It is governed by the same laws as terumah and must be eaten in a state of ritual purity.

I.e., it is not considered to have contracted impurity previously.

See Hilchot Sha’ar Avot HaTum’ah 11:15.

Hilchot Sha’ar Avot HaTum’ah 11:2. Both a person who immersed and impure hands are considered as secondary derivatives of impurity. Hence, they have no effect on the status of ordinary foods.

Which is bound by the same laws as terumah.

In his Commentary to the Mishnah (T’vul Yom 4:2), the Rambam mentions the women putting it into a container that is not susceptible to ritual impurity. The commentaries have questioned the need for this, since a secondary derivative of impurity does not impart impurity to a container.

These additions are made on the basis of the Rambam’s Commentary to the Mishnah (op. cit. 4:2).

See Hilchot Terumot 3:17; Hilchot Bikkurim 5:17.

I.e., there is no difference in law whether the person involved immersed that day or the utensil involved was immersed [the Rambam’s Commentary to the Mishnah (op. cit.:3)].

When the bottle that was immersed will regain a full state of purity.

The fact that the bottles were not totally pure at the time the wine was placed in them is not significant, as the Rambam proceeds to explain.

Tevel is a term used to refer to produce from which the necessary separations have not been made. In this instance, the wine in the bottles is considered as tevel and not terumat ma'aser, because, at the time that the designation was to take effect, the wine for which it was designated as terumat ma'aser no longer existed. Hence, the separation is not effective and it reverts to its initial status [the Rambam's Commentary to the Mishnah (op. cit. 4:4)].

For the separation was never effective, since the wine in the bottles no longer existed at the time the stipulation was to take effect.

In both instances, they are not able to regain purity until the seventh day after contracting impurity. Nevertheless, on the day they purify themselves, there is no difference between them and a person who purifies himself from a lesser impurity.

For the oil is like other ordinary food and is not disqualified when touched by a t’vul yom.

A man who experienced three successive discharges from his sexual organs similar to those resulting from a gonorrheal infection. See Leviticus, ch. 15; Hilchot Mechusrei Kaparah 2:1; Hilchot Metamei Mishkav UMoshav, ch. 1.

A woman who experiences uterine bleeding on three consecutive days outside her ordinary menstrual cycle. Her impurity is mentioned in Leviticus, op. cit.; Hilchot Mechusrei Kaparah 1:6; Hilchot Metamei Mishkav UMoshav, ch. 1.

Such individuals must count seven pure days in which no discharges were experienced. They may immerse themselves on the seventh day to regain purity. Nevertheless, their status is different from any other person who immerses himself, because if they experience a discharge during the day, before nightfall, all the seven days are disqualified retroactively. See Hilchot Metamei Mishkav UMoshav 5:9.

Taharot 3:2 also cites an opinion that maintains that the same ruling applies to wine that solidifies, but the Rambam does not accept it.

I.e., regardless of how many times they solidify and return to a liquid state, regardless of whether they are liquid or solid at the time a question arises. The rationale is even when they are solid, they are not totally solid and are considered as liquids even at that time [the Rambam’s Commentary to the Mishnah (Taharot 3:2)].
The Kessef Mishneh states that, although this idea is not explicit in the Rambam’s wording here, it is possible to interpret his statements in that vein. Indeed, it is necessary to do so. Otherwise, it is difficult to understand why he makes a distinction between these liquids and those mentioned in the following halachah.

Which are likely to solidify when they become cold [the Rambam’s Commentary to the Mishnah (op. cit.:1)].

This follows the interpretation of the Lechem Mishneh. Rav Akiva Eiger suggests that the term should be read as cheilev, i.e., fat.

Since they are not usually eaten while solid, in this state, they would not ordinarily contract impurity. If, however, one thinks of partaking of them in this state, they can be considered as foods. See Chapter 1, Halachah 20.

Which is always considered as a primary derivative.

The minimum measure of food that imparts impurity. See Chapter 4, Halachah 1.

The liquids are considered as having a different form than the solid mass. Hence, they are like a new entity and are, therefore, pure. They do not contract impurity from the solid mass, because it is less than the minimum measure necessary to impart impurity.

The bracketed additions (based on Chapter 6, Halachah 17) are necessary, because liquids do not contract ritual impurity unless they come in contact with food the size of an egg. Now, we are obviously not speaking about oversized grapes or olives, but a mass of these fruits.

For then the liquids would become impure because of his touch.

Other applications of this concept are found in Hilchot Terumot 12:11 and in Hilchot Issurei Mizbeiach 6:8.

Hence the fact that the fruit is impure does not change their status.

I.e., a woman after childbirth or a woman in the nidah state.

Hilchot Metamei Mishkav UMoshav 6:5-6, 8:2.

That were ordinary food [the Rambam’s Commentary to the Mishnah (Taharot 2:1)].

Thus impurity was not imparted to liquids.

Even though part of the leaf extends into the pot, since the part that was touched reaches outside the pot, it is considered as a distinct entity (ibid.). It must be emphasized that the other commentaries to the mishnah interpret this mishnah differently.

Because impure liquids are always considered as a primary derivative of impurity.

For impure liquids can impart impurity to keilim (Hilchot She’ar Avot HaTum’ah 7:1).

The impure person touched the leaf, but not the liquid.

If, however, it is smaller than an egg, it does not impart impurity to the liquids.

Because it is connected to them and even the slightest connection between liquids is sufficient to impart impurity.

This clause is a continuation of the mishnah cited above. In his commentary to that mishnah, the Rambam states that the mishnah is speaking about ordinary food which is not disqualified by a person who immersed that day. For that reason, in his explanation, he adds an additional factor: that the hands of the person who shook the pot were impure.
Here he interprets the situation differently, explaining that the vegetables in the pot were terumah, for terumah can be disqualified by a person who immersed.

As is food touched by a person who immersed that day. Although it is not known for certain that the person touched the food, when there is a doubt concerning impurity that was possibly imparted by a person who immersed that day, we rule stringently (Hilchot She’ar Avot HaTumah 10:5).

For liquids that were disqualified because they were touched by a person who immersed that day do not impart impurity to keilim (ibid.:3).

In which there were many grapes prepared to be crushed.

For a grape is smaller than an egg. Hence, it does not impart impurity to the grapes or to the wine. Since its stem is intact, no liquids will drip from that place [the Rambam’s Commentary to the Mishnah (Taharot 10:5)].

Our translation is taken from the Rambam’s Commentary to the Mishnah (ibid.:4).

Hence contact with that liquid will make the grapes susceptible to ritual impurity.

For, inevitably, there will be a small amount of liquid that drips from the place of the stem.

Since he touched them, they contracted impurity from him.

The Ra’avad adds that this ruling applies provided the impure person does not touch the liquid. The Kessef Mishneh states that this point is obvious and need not be mentioned.

See Halachah 2.

See Chapter 6, Halachah 16.

And his intent was to use the olives as kindling fuel.

Hilchot Sha’ar Avot HaTum’ah 7:1.

I.e., when the olives are heated, the oil they contain will flow out. Nevertheless, this oil is not considered impure, because it did not come in contact with impure food that was the size of an egg [Commentary to the Mishnah (Taharot 3:2)].

For impure liquids do impart impurity to keilim.

And thus their mass is certainly larger than an egg.

Because the oil will not have come into contact with an egg-sized portion of impure food (ibid.).

Moreover, in contrast to the oil mentioned in the previous halachah, in this instance, we are not concerned that the absorbed liquids will flow out when the oven is heated. Instead, it is assumed that they will be vaporized while within the wood [Rav Ovadiah of Bartenura (Machshirin 4:10).

I.e., one should not load the oven with this wood if he diverted his attention from his hands, in which instance, they are considered impure. Although water touched by these hands would not impart impurity to the oven, this safeguard should be taken for the reason mentioned by the Rambam. Once, however, people at large take this measure of care, even impure people will be more meticulous.

Where the olives are ground to extract their oil [the Rambam’s Commentary to the Mishnah (Taharot 9:8)].

This is speaking about an instance where the olives the carcass touches are not compressed into a mass the size of an egg. Hence the impure olives do not impart impurity to the pure ones.

Through contact with the carcass.

Because the olives became susceptible to impurity because of contact with the oil (ibid.).

Although the word of an unlearned person is not accepted with regard to the purity or impurity of his own produce, it is accepted with regard to the purity of produce belonging to others. See Hilchot Metamei Mishkav UMoshav 13:3.

Chapter 6, Halachah 16.

The bracketed addition was made because, according to the Rambam [see Chapter 6, Halachot 16-17], even if the carcass was touching an egg-sized portion of olives, as long as they are not compressed together, they do not impart impurity to other foods or liquids.

See Hilchot Metam’ei Mishkav UMoshav 10:1 for a definition of the term. As mentioned there, the impurity of an unlearned person is Rabbinic decree. He is not definitely impure. If a person is known to be definitely impure, all of the clusters in the winepress would be impure (Rambam Le’Am).

His touch renders those clusters which he touched as impure and they impart impurity to the clusters with which they are in contact.

From the Tosefta (Taharot 3:1), it appears that the intent is that the oil or wine was released from the olives or grapes originally, when those liquids were produce. Afterwards, when the pressure of the fruits was released, a small amount became reabsorbed in the waste products. When the impure people tread on the wastes, that liquid was released. Since the impure people did not touch it, it remains pure.

Because it contracted impurity when it was first expressed.

I.e., as a natural consequence of walking.

See a parallel ruling in Hilchot Parah Adumah 13:4.

In his Commentary to the Mishnah (Taharot 1:10), the Rambam emphasizes that the intent is not water designated for the ashes of the Red Heifer, but ordinary water that is being treated with the severity of consecrated foods.

The Rambam is describing an instance where the first loaf touches the second loaf without the liquids they contain touching each other. For that reason, due to the cherished nature of consecrated foods, this stringency was ordained. Had the liquids touched each other, the same ruling would apply with regard to ordinary foods and terumah as well, as the Rambam proceeds to state.

In his Commentary to the Mishnah (ibid.), the Rambam states that it is considered as if the liquid in the hollows touched each of the loaves. According to that logic, seemingly, the loaves themselves would be secondary derivatives and not primary derivatives as stated here (Mishnah Achronah).

As explained in Hilchot She’ar Avot HaTum’ah 7:5, if liquids that are primary derivatives of impurity touch other liquids, which touch other liquids, they are all still considered as primary derivatives of impurity. Indeed, even the 100th liquid in such a chain is still considered as a primary derivative.

See Hilchot Sha’ar Avot HaTum’ah 11:3.

This is a frequent occurrence in pottery made from clay and heated in a kiln [Rambam’s Commentary to the Mishnah (T’vul Yom 2:8)].

Note the accompanying diagram, taken from the drawings accompanying the above source.

I.e., a person who is a primary source of impurity placed his finger over the hole to the bubble.
The Ra’avad objects, stating that this law would apply even if a person who immersed that day (whose impurity is on a lesser level) would put his finger over the hole. The Kessef Mishneh explains that the Rambam (and his source) mention a primary source of impurity to teach that, in the situation described in the final clause, even a primary source of impurity does not impart impurity to the liquids in the jug.

As mentioned in Hilchot Tum'at Meit 20:1, a sealed covering prevents a container from contracting impurity. In this instance, however, since the hole extends into the inner space of the jug, it is not considered as sealed closed (ibid. 22:3).

Since the inner hole is higher than the outer hole, the level of the liquids in the bubble will sink below the inner hole and will not flow into the jug.