Gemara Sukka
Yeshivat Har Etzion

Shiur 01: INTRODUCTION – THE MITZVA TO DWELL IN A SUKKA

Rav Shmuel Shimoni

            The concluding folios of the second chapter of tractate Sukka (25a and on) deal with the mitzva to dwell in a sukka. In this shiur, we will not deal with the talmudic passages themselves, but rather we shall preface the discussion with a general introduction regarding the nature of the mitzva. We shall try to focus on two main questions: first, what is included in this mitzva, that is, which activities fall into the category of "dwelling"; and second, what is the status of this mitzva – obligatory or optional, as we shall see below. As in many other areas of Halakha, here too the laws governing the blessing that is recited over the mitzva may serve as a useful tool to clarify the nature of the mitzva itself.

THE COMPONENTS OF THE MITZVA OF DWELLING IN A SUKKA

            What is included in the mitzva to dwell in a sukka? The Baraita on p. 28b states:

"You shall dwell" – similar to [normal] residence. From here [the Sages] said: Throughout the seven days [of the festival], the sukka must be regarded as one's principal abode, and the house merely a temporary residence. How so? If a person has pretty dishes, he brings them up to the sukka; attractive linens, he brings them up to the sukka; he eats, drinks, and enjoys himself in the sukka, and he studies in the sukka.

            In other words, during the period of the holiday, a person must treat his sukka as his home, and do in it whatever he would normally do at home. While we know that the prohibition to engage in certain activities outside the sukka is limited to eating and sleeping, all aspects of normal residence are included in the mitzva (Rashi, at the beginning of the chapter, formulates this as follows: "The essence of dwelling in a sukka involves eating, drinking, and sleeping").

            What is the law regarding the blessing recited over the mitzva? Many Rishonim understood from the plain meaning of the Gemara (Sukka 46a) that a blessing should be recited every time one enters the sukka, for that too is part of the mitzva. For example, the Rif says as follows:

Whenever a person enters [the sukka] to dwell therein, he recites the blessing, "to dwell in the sukka." (22a in Alfasi)

            The prevalent custom, however, is only to recite a blessing over eating in the sukka. Thus, rules the Shulchan Arukh, end of sec. 639:

It is customary to recite a blessing over the sukka only at the time of eating.

            How are we to understand this custom? The Rosh writes in tractate Berakhot (1:13): "The Ri asked Rabbenu Tam whether one must recite a blessing over sleeping in the sukka, for the laws governing sleeping are more stringent than those governing eating, for one is permitted to snack outside the sukka, whereas napping outside the sukka is forbidden." Careful attention should be paid to the wording of the question. We appear to be commanded about dwelling in a sukka, that is to say, about normal residence, and two of the principal expressions of residence are eating and sleeping. There is, however, a difference between them, for incidental eating outside the sukka is permitted, whereas incidental sleeping outside the sukka is forbidden. Rava, however, understands this distinction as circumstantial, i.e., that regarding sleep there is no difference between incidental sleep and regular sleep. As Rashi explains: "There is no such thing as regular sleep, and there is no difference between incidental and regular sleep with respect to the sukka, for a person does not prepare himself for regular sleep, for at times he only has to nap a little and that suffices; therefore, that is his sleep." The Ri's question assumes that sleeping is a more significant expression of residence than is eating, though the proof for this assumption is problematic.

            The Ri himself answered his question as follows: "One does not recite a blessing over sleeping [in the sukka] because perhaps he will be unable to fall asleep." That is to say, fundamentally speaking, there is room to require a blessing over sleeping in the sukka, but we are concerned about a blessing recited in vain, for the person may not manage to fall asleep. As we shall immediately see, Rabbenu Tam appears not to have been concerned about this problem. It stands to reason that he understood that there is no room here for concern about a blessing recited in vain, because the blessing is recited over the very trying to go to sleep, so that it does not matter if he does not manage to fall asleep. The Vilna Gaon relates to this dispute in his commentary to the Shulchan Arukh (432, 2), arguing that it corresponds to a similar dispute among the posekim regarding bedikat chametz (searching the house for chametz) whether it is necessary to leave out small pieces of chametz in order to avoid the possibility that the blessing will have been recited in vain, or whether the blessing is recited over the search for chametz itself, and so such concern does not exist. He adduces proof for the position of Rabbenu Tam from the law of birkat ha-mapil which a person recites before going to sleep, there being no concern that perhaps he will be unable to fall asleep. [It should be noted, however, that some members of the Brisker dynasty were indeed concerned about this problem, and therefore refrained from reciting the ha-mapil blessing]. In any event, the Vilna Gaon implies that we are dealing here with a general dispute regarding blessings. It seems more reasonable, however, that the Ri and Rabbenu Tam disagree about how sleeping constitutes an element of the mitzva of dwelling in a sukka – is it the sleep itself that constitutes the mitzva, or is it the fact that the person relates to the sukka as if it were his house, and therefore when he goes to sleep, he does so in the sukka.

As was stated above, Rabbenu Tam disagreed with the Ri's explanation, and therefore proposed an explanation of his own: "But Rabbenu Tam answered him that [whatever elements of] the mitzva of sukka that a person fulfills between one meal and the next, for example, sleep, enjoyment, and study - the blessing 'to dwell in a sukka' that he had recited over the meal exempts him from reciting [another] blessing over them." Rabbenu Tam agrees with the fundamental assumption that sleeping in the sukka requires a blessing, but he understands that the blessing recited over the meal covers his sleep as well. The Taz and the Mishna Berura explained the aforementioned ruling of the Shulchan Arukh in light of Rabbenu Tam's explanation, and concluded that a person who is fasting (e.g., a fast observed on account of a bad dream) and not eating is obligated to recite a blessing over his very entry into the sukka.

According to Rabbenu Tam, why is the blessing recited over the meal, and not over sleep? As we noted above, the Ri's question is based on the assumption that sleep is more severe than eating, and constitutes a more important expression of dwelling. There is no explicit indication in the words of Rabbenu Tam that he disagrees. One can certainly understand from them that even if sleep is more fundamental, eating is a more clearly-defined activity over which a blessing may easily be recited and thus exempt the other expressions of dwelling from a blessing. Rabbenu Tam's position, however, is also cited by the Rosh in Sukka¸ and there the formulation is clearer: "Rabbenu Tam explained that [the blessing is recited over the meal] because the primary expression of fixed residence that a person has in a sukka is eating, but the other forms of enjoyment and sleep in a sukka are subordinate to eating, and it exempts them" (4, 3). Here it is explicitly stated that "dwelling" in a sukka finds its primary expression in eating.

This idea also finds expression in a tannaitic opinion that was not accepted as final law: "Rabbi Eliezer says: A person is obligated to eat fourteen meals in the sukka, one during the day and one at night… What is Rabbi Eliezer's reasoning? 'You shall dwell' – similar to [normal] residence. Just as residence [in the house] – one [meal] during the day and one at night, so too in the sukka – one [meal] during the day and one at night" (27a). Why does Rabbi Eliezer obligate a person to eat in the sukka, but not to sleep there? It stands to reason that he too understood that the focus of dwelling lies in eating. It must be admitted, however, that the Ri's position is much easier to understand – for surely a person eats on occasion outside of his house, whereas sleep is an activity that is clearly connected to the home.

Thus far we have been working with the assumption that "teshvu" implies residence. The literal meaning of the term, however, is sitting. At first glance, it would seem that in our case this meaning is irrelevant, as the Rambam states: "How so the mitzva of dwelling in a sukka? A person should eat, drink, and live in a sukka all seven days both during the day and at night, as he resides in his house the rest of the days of the year" (Hilkhot Sukka 6:5). It seems, however, that the Rambam understood that alongside the borrowed sense of the term yeshiva, i.e., "dwelling," the literal sense of the term – "sitting" – is pertinent here as well:

Every time he enters to sit in the sukka all seven days, before he sits down, he recites the blessing, "Who has sanctified us with His commandments and commanded us to sit in a sukka." On the night of the first festival, he recites a blessing over the sukka and afterwards he recites a blessing over the season [= shehecheyanu], and he arranges the blessings over a cup [of wine]. Thus, he recites the kiddush standing, recites the blessing, "to sit in a sukka," sits down, and afterwards recites the blessing over the season. This was the custom of my rabbis and the rabbis of Spain to stand for the recitation of kiddush on the first night of Sukkot, as we have explained.

            According to the Rambam, in order to recite the blessing over the mitzva "prior to its performance," a person should recite the blessing while standing and only afterwards sit down, because the sitting down is the commanded action. Many have raised objections against the Rambam. We will cite here the words of the Rosh, who objected to the Rambam's interpretation of the term "yeshiva":

According to him, a person should recite the blessing before he enters [the sukka], for the mitzva is entering [the sukka], and not sitting in it. For would he eat standing up he would have to recite a blessing over the sukka. Without a doubt then since the mitzva of sukka consists of eating and enjoyment, if he recites the blessing after he sits down, it is still called "prior to its performance"… And "in booths teshvu" means "you shall stay there," as in: "And the nation stayed [va-yeshev] in Kadesh." And also: "You shall stay [teshvu] at the entrance to the Tent of Meeting." And leshev be-sukka also means to stay in the sukka, and therefore it is still called "prior to its performance" if he recites the blessing after he sits down. (Rosh, Sukka 4, 3)

            As we have seen, the Rambam also understands that the mitzva of yeshiva does not relate exclusively to sitting in a chair, but according to him, the clearest expression of fixed residence in a sukka is achieved through sitting in the literal sense, and therefore the blessing should be recited immediately prior to sitting down. See also Torah Temima (Vayikra 23:42) who discusses the Rambam's opinion at length, proposing that one who eats in the sukka in a standing position has not fulfilled his obligation. Needless to say, this is an exceedingly novel position.

SUKKA ALL SEVEN DAYS – A MITZVA THAT IS "FULFILLABLE" OR OBLIGATORY?

            The Acharonim often distinguish between obligatory mitzvot - which a person is obligated to fulfill, and if he fails to do so, he nullifies a positive precept – and "fulfillable" mitzvot – which a person is under no obligation to fulfill, but if he does so, he fulfills a mitzva. Practically speaking, a distinction must be made between three different models:

1)         A mitzva that a person is under obligation to perform, that obligation being out of his control, like the donning of tefilin.

2)         A mitzva that a person is under no obligation to perform, but if he performs it, he fulfills thereby a mitzva, like the mitzva of ritual slaughter, according to the Rambam at the beginning of Hilkhot Shechita.

3)         A mitzva that a person is not obligated to pursue, but if he chooses to engage in a particular activity, he is obligated to fulfill the mitzva. Thus, for example, a person is not obligated by Torah law to wear tzitzit, but if he wishes to wear a four-cornered garment, he is obligated to outfit it with tzitzit.

Into which category does the mitzva of sukka fall? To clarify the question, we are not talking about the status of the obligation to eat in a sukka on the first night of Sukkot – a topic that we will deal with in the near future. Rather, we are talking about the other days of Sukkot, during which a person is not obligated to eat or sleep, but if he engages in those activities, he must do so in a sukka. At first glance, the mitzva of sukka falls into the third category – if a person opts to eat, he must do so in a sukka. The Minchat Chinukh defined the matter as follows:

There are two kinds of positive precepts: One that is an obligation falling on the head of every man of Israel like tefilin, etrog, and the eating of matza. Such a mitzva – if a person fulfills it, he does the will of the Creator, blessed and exalted be He, because this is what the King, blessed be He, decreed. And if he neglects the mitzva and fails to don tefilin or take a lulav, he nullifies the mitzva and acts in opposition to His will, blessed be He, and he will surely be punished. And there are mitzvot that one is not obligated to perform, like tzitzit, for the Torah did not obligate a person to wear a four-cornered garment, and if he so desires, he may go about without a four-cornered garment, and this is not against the will of the Creator, blessed be He. If, however, he brings himself to obligation, intentionally wearing a four-cornered garment in order to fulfill the mitzva of tzitzit, this is the good and righteous path. The rule is that if he fulfills this mitzva, he does the will of the Creator, blessed be He, but if he fails to fulfill the mitzva, he does not violate His will, but merely does not fulfill the mitzva. So too, regarding this mitzva, namely, sukka, there are two parts to the mitzva. That is to say, on the first night of Sukkot, there is a positive precept to eat the measure of an olive in a sukka, and a person is obligated to look for a sukka, and it does not help that he does not want to eat, because he is obligated to eat, as with matza or tefillin. And if he fails to fulfill the positive precept on the first night, he acts against God's will, blessed be His name. But on the rest of the nights and days, if he does not want [to eat], he may abstain from eating and not sit in a sukka, and he is bound by no obligation, as with tzitzit. If, however, he eats, there is a positive precept to eat in a sukka and he fulfills His will, blessed be He, but if he does not eat, there is no obligation to do so. And also regarding these two mitzvot, there is a case where he nullifies the mitzva and acts against His will, like one who fails to don tefillin. For example, if he wears a four-cornered garment without outfitting it with tzitzit, then he violates the mitzva. And so too if he eats a major repast outside the sukka, he violates the mitzva. The rule is that if a person performs a mitzva, he fulfills the mitzva in all cases, and does His will, blessed be He. And there is a case where he fails to perform a mitzva and thus violates His will, e.g., where he wears a four-cornered garment [without tzitzit] or eats a major repast outside the sukka. And there is a case where he fails to perform a mitzva, but also does not violate [anything], e.g. where he does not wear the garment or does not eat anything. This is evident. (Minchat Chinukh sec. 325, no. 10)

            In other words, the mitzva of dwelling in a sukka all seven days has the status of a fulfillable mitzva, if a person decides to eat in the sukka, and there is a prohibition to nullify the positive precept by eating outside the sukka. We will see later that the Minchat Chinukh maintains that this prohibition does not absolutely correspond to the non-fulfillment of the mitzva. That is to say, there can be situations in which a person eats without fulfilling the mitzva, but nevertheless he does not violate the prohibition of nullifying the mitzva. What is important to emphasize here, however, is how, in my humble opinion, one is not to understand the matter. R. Yosef Engel, z"l, in his book, Atvan De-oraita (kelal 11) restated the Minchat Chinukh's position as follows:

Eating in the sukka is not pleasing and desired in itself, for were that the case, it would not be right to leave that eating to the will of the individual, so that it is optional. Perforce, then, the intention of the mitzva lies exclusively in the negation, that when a person eats, he must not eat outside the sukka, and eating outside the sukka is what is not pleasing. But eating in the sukka in itself is not at all pleasing or desired.

            According to this formulation, the mitzva of dwelling in a sukka is not really a mitzva, but a prohibition – one is forbidden to eat outside of a sukka. The sukka serves as sort of a matir (factor of allowance) for this prohibition.

            This is also the implication of the Avnei Nezer (Orach Chayyim, no. 481), who used this understanding to reconcile an objection raised against Rabbenu Tam:

Rabbenu Tam maintains that a woman may not make tzitzit nor bind the species accompanying the lulav, because she is not obligated [in those mitzvot], just as she is disqualified from writing tefilin, since she is not obligated in the tying. This is astonishing, for how is this different from sukkat GaNBaK [= the initial letters for the Hebrew words for "gentiles, women, cattle and Samaritans"; in other words, a sukka made by a gentile is fit]… It follows from this that regarding a sukka, we can say that the sukka permits eating, enjoyment, and sleep… And this is the implication of our passage that likens sukka to matza which all seven days is optional. It is explicit then that it is merely forbidden to eat outside the sukka, just as it is forbidden to eat chametz. And therefore there is no objection from sukkat GaNBaK which is fit, for it comes merely to allow [eating and the like], and therefore need not be made by one who is obligated.

According to the Avnei Nezer, a mitzva-object (cheftza shel mitzva) can only be created by one who is bound by the obligation (bar chiyyuva), but a sukka is not a mitzva-object. It is merely a matir, and a matir does not require a bar chiyyuva.

This formulation, however, seems to be exceedingly problematic – it would seem that we are not dealing here with prohibitions or prohibitions following from positive precepts, but rather with a mitzva, which like many other mitzvot includes a prohibition to nullify it. [As we shall see below, the Atvan De-oraita himself rejects this understanding of sukka, but he accepts it regarding tzitzit. But this too is very difficult; what value is there in wearing a four-cornered garment, if all we have here is a prohibition to wear such a garment without tzitzit? Is there any value in buying meat in order to eat it without milk?]

            Thus far, we have been working on the simple assumption that the mitzva of dwelling in a sukka is not a positive mitzva. Let us now analyze a discussion in the framework of which there arise positions that question this assumption.

            The Gemara in Sukka 27a derives the law that dwelling in a sukka on the other days is optional by way of an analogy to matza on Pesach:

Like residence, just as residence – if he wishes, he eats, if he wishes, he does not eat, so too a sukka – if he wishes, he eats, if he wishes, he does not eat. If so, even on the first night of the festival! Rabbi Yochanan said in the name of Rabbi Shimon ben Yehotzadak: It says here "the fifteenth," and it says "the fifteenth" regarding Pesach. Just as there – the first night is obligatory, from then on it is optional, so too here – the first night is obligatory, from then on it is optional. And from where do we know [the law] there? The verse states: "In the evening, you shall eat matzot" – Scripture established it as an obligation.

            This comparison brought the Rishonim to ask the following question: Why is a blessing recited over eating in the sukka all seven days, but not over eating matza on Chol Ha-mo'ed of Pesach? The question assumes that the gezera shava between the two teaches us about a similar level of obligation, and thus the law should be the same regarding the blessing. If we further sharpen the matter, the question assumes that just as eating in the sukka all seven days of Sukkot is a fulfillable mitzva, so too eating matza all seven days of Pesach. This is the position attributed to the Vilna Gaon (Ma'ase Rav, no. 185), and stated explicitly by the Chizkuni (Shemot 12:18). In light of this, the Netziv (Responsa Meishiv Davar, II, no. 77) considered the possibility that a blessing recited over matza all seven days should not be considered as a blessing recited in vain, and other Acharonim related (negatively) to the custom that was common in certain communities to recite a blessing, but the clear assumption of the Rishonim was that a blessing should not be recited.

            The author of the Sefer Ha-mikhtam related to this question on p. 27a, bringing two different answers. One answer explicitly rejects the assumption concerning matza, and established that there is no fulfillment of a mitzva of eating matza all seven days:

Rabbenu Shemuel bar Shelomo, ztz"l, answered that matza is different, because eating it on the other days is not for the sake of the mitzva of matza, but for the sake of his body to satisfy his hunger, because he cannot fill himself with chametz. It is like someone who fills himself with the meat of a kosher animal because he is unable to eat the meat of a non-kosher animal, but does not recite a blessing, "Who has sanctified us with His commandments and commanded us to eat kosher meat." But a person certainly does not dwell in a sukka for the sake of his body, or to satisfy his hunger, but only to fulfill the mitzva, and therefore he must recite a blessing.

            If we see in the eating of matza nothing more than an optional activity, why is it so clear to us that sitting in a sukka constitutes a mitzva? The Mikhtam explains that in contrast to the eating of matza, which fundamentally is not a halakhic act, when a person eats on Sukkot, the Torah commands him to perform a clearly halakhic act: to enter a sukka and eat there, and thus it must be a mitzva.

The Mikhtam also brings another answer that was offered already by the Ba'al Ha-ma'or at the end of tractate Pesachim. This answer does not reject the question's assumption that even the eating of matza involves the fulfillment of a mitzva, but rather it argues that a blessing may only be recited over a positive mitzva. Thus, he proposes the highly novel idea that sukka all seven days of the holiday is a positive mitzva. How can this be? Surely a person is not required to eat so that he can fulfill the mitzva of sukka? The Ba'al Ha-ma'or explains as follows:

It may be answered: Because on the other days [of Pesach] a person can go without eating matza and sustain himself on rice and millet and all kinds of fruit. This is not the case regarding a sukka, for a person cannot go for three days without sleep and so he must sleep in the sukka and enjoy himself there…. This is the reason that we recite a blessing over the sukka all seven days, but we do not recite a blessing over matza all seven days. (Ba'al Ha-ma'or, Pesachim 26b-27a in Alfasi)

            The Ba'al Ha-ma'or relies on what the Gemara says in several places that a person cannot go for three consecutive days without sleep. According to him, this means that dwelling in a sukka is a positive mitzva, for willy-nilly a person is forced to decide between fulfilling it and nullifying it. While this is true only with respect to sleep, sleep is only one practical branch of the mitzva of dwelling in a sukka, which as a mitzva is now defined as a positive mitzva. [The Birkei Yosef in sec. 639 writes: "And according to R. Zerachya ha-Levi who answered that the obligation to sleep in a sukka is absolutely necessary, and this is the main reason for the obligation to recite a blessing, as I have written, one must be exceedingly careful about sleeping, for in addition to the obligation, all the blessings are essentially because of the sleep."]

Two objections may be raised against this explanation:

1)         One question was raised by the Tashbetz in his responsa (I, no. 100). The assumption that a person cannot go without sleep for three days is brought in the Gemara in Sukka 53a:

Rabbi Yehoshua ben Chananya said: When we celebrated Simchat Bet Ha-sho'eva, our eyes did not see sleep…. Is this so? But surely Rabbi Yochanan said: I swear that I will not sleep for three days, we flog him and he may go immediately to sleep! Rather he said as follows: We didn't taste the taste of sleep, for we dozed off on each other's shoulders.

            In light of this, the Tashbetz argues that one can avoid sleeping in a sukka by restricting oneself to dozing:

If you say: They are not similar, because sukka all seven days even though it is optional, he cannot exempt himself from it all seven days, because it has been established that one who swears that he will not sleep for three days is flogged and then immediately goes to sleep – this is nothing… Even for seven days it is possible to doze a little on the shoulders of one's fellow as they used to do at the Simchat Bet Ha-sho'eva, as it is stated in chapter He-Chalil… And even though we maintain (26a) that a nap requires a sukka, even if he puts someone else in charge of his sleep – that is by rabbinic decree, because of a concern lest he be drawn into [deep] sleep. But not that it cannot be so. This being the case, it is totally optional to sit in the sukka all seven days.

2)         A second objection touches upon the very essence of the Ba'al Ha-ma'or's position: Why should the circumstantial fact that a person cannot go three days without sleep define the mitzva as a positive mitzva? He is forced to sleep by nothing more than circumstances. The Maharam Chalawa, at the end of his novellae on Pesachim, cites the words of the Ba'al Ha-ma'or. His formulation implies that while in essence the mitzva is not defined as a positive mitzva, since at the bottom line the Torah forces a person to dwell in a sukka, one can recite the words, "Who has sanctified us with His commandments and commanded us to dwell in a sukka," which is not the case with matza all seven days of Pesach. According to this, the Ba'al Ha-ma'or did not propose a novel understanding of the essence of the mitzva of sukka all seven days.

The Atvan De-oraita at the end of the aforementioned section also sees sukka all seven days as a positive mitzva, but formulates the position differently than did the Ba'al Ha-ma'or:

The position itself of the aforementioned Minchat Chinukh, who writes that sukka is exclusively a negative mitzva – it seems, in my humble opinion, that this is not true. Rather, sukka is a positive and independent mitzva, for the Torah wants us to live for seven days in a sukka, just as we live all year long in the house. As they said: "You shall dwell" – similar to [normal] residence. The fact that if a person wishes, he doesn't have to eat or sit in a sukka, that is because that is the essence of residence, that occasionally a person goes out or to the market, and only when he wishes to eat, drink or sleep, does he eat, drink and sleep exclusively in his house. This is the idea of residence in his house, and thus the Torah wanted us to live for seven days in a sukka. Thus when the Torah asks for residence in a sukka, it is asking for a desired and positive thing.

            This explanation posits that while indeed eating in the sukka is not a positive mitzva, the truth is that the mitzva is not eating in the sukka. The mitzva is dwelling in the sukka. A person must turn his sukka into his home for all seven days of the festival, and the practical expression of this is that all eating and sleeping must take place in the sukka.

            In conclusion, let us note that the comparison between a sukka and a house raised a certain difficulty for one of the Rishonim:

"You shall dwell" – similar to [normal] residence. Just as residence – if he wishes, he eats, if he wishes, he does not eat, so too a sukka – if he wishes, he eats, if he wishes, he does not eat. Now I fail to understand why we don't say: Just as residence – if he wishes, he eats in his house, if he wishes, he eats out of his house, in his courtyard or on his roof, so too a sukka. (Responsa Maharach Or Zaru'a, no. 196)

   The answer to the Maharach Or Zaru'a's question, it would seem, must be that the transition from the optional house to the residence of mitzva creates a difference: A person is commanded to perform his domestic activities in the sukka, which is no longer his personal space which he can abandon at will.

            In our next shiur, we will deal with the law that one who is engaged in a mitzva is exempt from other religious duties. Please study the Mishna on p. 25a and the Gemara at least until p. 25b, "eima lo tzerikha," and if possible until 26a, "sheluchei mitzva anan u-peturin" (without getting involved in the issue of mitzta'er), [Tosafot 25b, s.v. mishum]. In addition:

1)         Avot 2:1, and Rambam's commentary ad loc.

2)         On our passage: Tosafot 25a, s.v. sheluchei; Ran 11a in Alfasi, s.v. matnitin, ve-ikka, u-mihu; Ritva, s.v. matnitin.

3)         [Shulchan Arukh 475:5; Mishna Berura, no. 39, Sha'ar ha-Tziyun.]

4)         Responsa Maharach Or Zaru'a, no. 183.

Young men traveling to study Torah are exempt from all mitzvot as long as they are in their master's house, like Rav Chisda and Rabba bar Rav Huna who were exempt as long as they had not yet heard the lecture. Nevertheless, if they wish to recite a blessing over tzitzit and tefilin, they may do so, just like women. For Rabbenu Tam, of blessed memory, ruled that women may recite a blessing over any time-bound positive commandment. And, therefore, they can blow shofar for those who are obligated [in that mitzva]. And we do not say that someone who is exempt, even by rabbinic law, cannot come and discharge the obligation of someone who is obligated, for all of Israel are responsible for one another. As it is stated in Rosh ha-Shana that regarding all blessings, even though a person has already fulfilled his own obligation, he can discharge the obligation of others.

(Translated by David Strauss)