Talmud - Sukkah 7a סוכה ז׳ א׳

And let him position the wall measuring one handbreadth opposite the wall that emerges like the diagonal line formed by the end of the furrows as the field gradually narrows. This third partition would represent the third side of a triangle and would make the sukka appear more like a full-fledged structure, as the diagonal would represent closure of both unwalled directions. Rav was silent and did not respond.

It was also stated that Shmuel said in the name of Levi: He positions it at the end of one of the standing walls opposite the wall that emerges from the other end of that wall. And similarly, they rule in the study hall: He positions it at the end of one of the standing walls opposite the wall that emerges from the other end of that wall.

Rabbi Simon said, and some say it was Rabbi Yehoshua ben Levi who said, that the third wall is positioned differently. He establishes for the third side a wall that measures an expansive handbreadth, measured with the fingers spread apart, which is slightly larger than a standard handbreadth. And he then positions it less than three handbreadths from and adjacent to the wall opposite the second wall. And the legal status of any item positioned less than three handbreadths from and adjacent to the wall is like an item joined to that wall. In this way, the handbreadth-wide wall is joined to the adjacent wall, and it is as if it is a wall of four handbreadths, which is the majority of the minimum measure of the wall of a full-fledged sukka, seven handbreadths.

Rav Yehuda said: A sukka constructed like an alleyway, with two parallel full-fledged walls, is fit, and with regard to that third wall that measures one handbreadth, he positions it adjacent to one of the walls in any direction that he chooses, as it is merely a conspicuous marker.

Rabbi Simon said, and some say it was Rabbi Yehoshua ben Levi who said: In the case of a sukka built like an alleyway open on two ends, a third wall measuring a single handbreadth is insufficient. Rather, one establishes for the third side a board with a width of four handbreadths and a bit and positions it less than three handbreadths from and adjacent to either wall, as a wall on either of the open ends. And the legal status of any item positioned less than three handbreadths from and adjacent to the wall is like an item joined to that wall. The result is a full-fledged seven-handbreadth sukka wall.

The Gemara asks: What is different there, in the case of two attached walls, where you say that a wall with the dimension of an expansive handbreadth suffices to complete the third wall, and what is different here where you say that it requires a board that measures four handbreadths and a bit? The Gemara answers: There, where there are two walls in the standard sense, as they are attached forming a type of structure, it is sufficient to have the third wall measure an expansive handbreadth in order to render the sukka fit; however, here, where there are not two walls in the standard sense, as they are not attached, if there is a board that measures four handbreadths as the third wall, yes, it is fit, and if not, no, it is unfit.

Rava said: And the sukka consisting of two adjacent walls with a third wall measuring one handbreadth is permitted and fit only if the third wall is in the form of a doorway. One can render the sukka fit only by splitting the one-handbreadth wall and attaching one half to the standing wall and one half across from the other wall that emerges from the standing wall, and then placing a pole across the two halves. By creating the form of a doorway, that third wall becomes like an open gate, which is considered a halakhic partition.

Some say that Rava said: And a sukka consisting of two adjacent walls is also permitted and fit if the third wall is in the form of a doorway. In other words, Rava does not reject the remedy of the expansive-handbreadth wall suggested by Rabbi Yehoshua ben Levi; rather, he suggests an alternative.

Some say a third version of that which Rava said: And a sukka consisting of two adjacent walls, even with a third that is an expansive handbreadth wide as suggested by Rabbi Yehoshua ben Levi, also requires the form of a doorway to be fit. In other words, in addition to Rabbi Yehoshua ben Levi’s remedy, one must also create the form of a doorway to render the sukka fit.

The Gemara relates: Rav Ashi found Rav Kahana establishing his sukka, which had two adjacent walls, and establishing a third wall that was an expansive handbreadth wide and establishing the form of a doorway as well. Rav Ashi said to him: And does the Master not hold in accordance with that opinion of Rava, as Rava said: And the sukka is also permitted and fit if the third wall is in the form of a doorway? Why are you establishing a wall that is an expansive handbreadth wide as well? Rav Kahana said to him: I hold in accordance with the other version of the opinion of Rava, as Rava said: And the sukka also requires the form of a doorway, in addition to the expansive handbreadth, to be fit.

§ It is taught in the Tosefta that if the sukka has two walls in the standard sense and a third wall that measures one handbreadth, it is fit. Rava said: And likewise with regard to Shabbat that occurs during the festival of Sukkot, since it is considered a wall with regard to the halakhot of sukka it is considered a partition with regard to the halakhot of Shabbat. Were one to construct a sukka in that manner in a public domain adjacent to the entrance to his house, its legal status would be that of a private domain and one would be permitted to move objects from it to his house and vice versa on Shabbat that occurs during the Festival. However, that structure is not considered a private domain on any other Shabbat.

Abaye raised an objection to Rava’s opinion from a baraita: And do we say that this principle: Since it is considered, etc., applies in this area of halakha? But isn’t it taught in a baraita: The specifications of the wall of a sukka are like those of a partition with regard to the halakhot of Shabbat. Just as with regard to the halakhot of Shabbat, one forms a partition by establishing adjacent reeds, so too, one forms the wall of a sukka in the same manner, provided that the gap from one reed to another will not be as much as three handbreadths. If the gap is three handbreadths or greater, the legal status of the reeds is that they are not considered joined.

But the stringency of the halakha with regard to Shabbat goes beyond the stringency of the halakha with regard to sukka, in terms of the criteria for effective partitions, as with regard to Shabbat, carrying is permitted only in a case where the total of the standing segments of the partition, the actual wall, is greater than the total of the breached segments of the partition, the gaps that are less than three handbreadths. That is not so with regard to the sukka, where, even if the breached segments total more than the standing segments, e.g., a sukka consisting of two walls in which there are gaps and a third wall measuring only a single handbreadth, it is still fit.

The Gemara analyzes the baraita. What, isn’t the baraita teaching that the stringency with regard to Shabbat that occurs during the festival of Sukkot goes beyond the stringency with regard to the rest of the festival of Sukkot? And apparently, we do not say the principle: Since it is considered a fit partition for sukka let it also be considered a fit partition for Shabbat. This is difficult according to Rava, in whose opinion that principle is applied in this case.

Rava rejects that interpretation of the baraita. No, the baraita is teaching that the stringency with regard to Shabbat in general goes beyond the stringency with regard to Shabbat that occurs during the festival of Sukkot. On Shabbat during the festival of Sukkot, a partition where the total of the breached segments of the partition is greater than the total of the standing segments is effective, as, since it is effective as a wall in a sukka, it is effective as a partition for Shabbat as well. That is not the case on Shabbat during the rest of the year, when a partition of that sort is ineffective on Shabbat.

Abaye asked: If it is so that the distinction in the baraita is not a fundamental distinction between the halakhot of sukka and the halakhot of Shabbat, but is instead a distinction between the halakhot of Shabbat in general and the specific case of Shabbat during the festival of Sukkot, then let the baraita also teach a novel distinction involving Shabbat that occurs during the festival of Sukkot. The stringency with regard to sukka in general during the rest of Sukkot goes beyond the stringency with regard to sukka on Shabbat that occurs during the festival of Sukkot, as a sukka in general consisting of two parallel walls, like an alleyway, requires that its third wall measure an expansive handbreadth, while a sukka on Shabbat does not require an expansive handbreadth for this purpose, and it is sufficient for the third wall to be established with a side post ten handbreadths high and any width.

Since the side post is effective as a partition with regard to the halakhot of Shabbat, it should also be effective as a wall with regard to the halakhot of sukka although it is less than one handbreadth wide, as you are the one who said: If one placed roofing over an alleyway which has a side post on one of the open ends to permit carrying in that alleyway on Shabbat, it is fit as a sukka for that same Shabbat, although it would not be fit during the rest of the week of the Festival.

Rava replied to him: That is indeed my statement; however, the fact is that the baraita does not cite that distinction, because it is not necessary to state that there are circumstances in which the general halakhot of sukka are stricter than its halakhot on Shabbat, as there is no novelty in the concept that the halakhot of partitions on Shabbat should apply to a sukka. Now that we say that halakhot may be derived from a leniency to a stringency, as a halakha that applies to sukka, which is a positive mitzva, is applied to the halakhot of Shabbat, which is a stringent prohibition punishable by karet; then from a stringency, the halakhot of Shabbat, to a leniency, all the more so may halakhot be derived. Therefore, there is no reason for the baraita to mention that distinction explicitly.

§ Apropos roofing over an alleyway, the Gemara elaborates about the matter itself. Rava said:

Traduction : The William Davidson digital edition of the Koren Noé Talmud, with commentary by Rabbi Adin Even-Israel Steinsaltz.

Succah 7a explores rabbinic debates over the proper placement and minimum size of a third wall needed to validate a sukkah built like an alleyway.