When they disagree is according to the opinion of Rav. Abaye holds in accordance with the opinion of Rav: The edge of the roof descends and seals both in the portico in the field and in the portico that one roofed as a sukka. And Rava could have said to you: Rav stated his opinion only there, with regard to a portico in the field, because the partitions formed by the descent of the edge of the roof are partitions established for the portico. However, here, in the case of a sukka, where the partitions formed by the descent of the edge of the roof are not partitions established for the portico, no, Rav would not say that the edge of the roof descends and seals.

The Gemara cites another proof. We learned in the mishna: With regard to a courtyard that is surrounded on three sides by a portico, if there are four cubits beneath the unfit roofing, the sukka is unfit. The Gemara asks: And why is the sukka unfit? Let us say that the edge of the roof descends and seals, forming a fit partition at the point where the roofing of the sukka begins?

Rava interpreted the mishna in accordance with the opinion of Abaye: It is a case where one equalized the level of its roofing, i.e., the roofing of the sukka with the level of the roof of the portico. Since the edge of the roof of the portico is not visible inside the sukka, the principle: The edge of the roof descends and seals, does not apply.

In Sura, they would teach this halakha in that language cited above. In Pumbedita they would teach it differently: If one roofed a portico that does not have posts on its open side, everyone agrees that the sukka is unfit. In the case of a portico that has posts less than three handbreadths apart on its open side, Abaye said: The sukka is fit, and Rava said: The sukka is unfit. Abaye said: The sukka is fit, as we say that the principle of lavud applies here; the posts are joined and form a partition for both the portico and the sukka in the courtyard outside the portico. Rava said: The sukka is unfit, as we do not say that the principle of lavud forms a partition for the sukka. The Gemara concludes: And the halakha is ruled in accordance with the first version.

The Gemara relates: Rav Ashi found Rav Kahana, who was placing roofing for a sukka atop a portico that did not have posts. He said to him: Doesn’t the Master hold in accordance with that which Rava said: If it has posts, the sukka is fit; if it does not have posts it is unfit? How can you use this as a sukka? Rav Kahana showed him that in this sukka the disparity between the sukka and the portico was visible from the inside and even from the outside. From outside, the portico and the sukka appeared to be one continuous structure. However, from inside, one of the walls of the portico was visibly thicker than the wall of the sukka, and that one handbreadth thickness serves as the third wall of the sukka.

Alternatively, in this case that disparity was visible from the outside and even from the inside. The exterior walls of the portico and of the sukka were not even. From the outside, it was plainly discernible that they were two separate structures. However, from the inside the sukka appeared to be a direct extension of the portico with no post protruding. In both cases, the protruding segment serves as the third wall of the sukka, which measures one handbreadth, and the sukka is fit.

This distinction is as it was stated in the context of merging courtyards that open into an alleyway that is open on one side to allow carrying there on Shabbat, one must establish a side post on one side of its opening: Any object that protrudes and is visible from outside the alleyway but is even with the wall on the inside of the alleyway has legal status of a side post, since it can be discerned from the outside. And the provisions that apply to a side post in the case of merging of alleyways are the same as those that apply to posts in the case of sukka. Rav Kahana’s sukka was essentially a portico with a post, and was fit for use as a sukka.

§ It was taught in the Tosefta: Fit roofing that consists of different kinds of agricultural waste products that extend from the sukka has the legal status like that of the sukka. The Gemara asks: What is the meaning of: Waste products that extend from the sukka? Ulla said: Branches that extend behind the sukka and are not limited to the area within the sukka walls.

The Gemara asks: But don’t we require three walls to render an area covered with roofing a fit sukka? The Gemara answers: It is referring to a case where there are three walls. The two side walls of the sukka do not end at the middle wall between them; rather, they too extend behind the sukka, forming a second sukka. The Gemara asks: But don’t we require seven by seven handbreadths as the minimum area for fitness of a sukka? The Gemara answers: It is referring to a case where there is the requisite minimum area. The Gemara asks: But don’t we require that its shade exceeds its sunlight? The Gemara answers: It is referring to a case where there is more shade than sunlight.

After noting that the sukka has three walls, the requisite area, and sufficient shade, the Gemara asks: If so, what purpose is there to state this halakha? The fact that this sukka extends from another is not relevant. The Gemara answers: Nevertheless, there is a novel element in this halakha. Lest you say that since, as evidenced by the placement of the connecting middle wall, these walls were initially established for inside the original sukka but not for outside the original sukka; and therefore you say no, the middle wall cannot be considered a wall for the additional sukka, Ulla teaches us that the initial intention is not relevant.

Rabba and Rav Yosef both say with regard to the case in the Tosefta: Here, it is referring to a case with branches that extend before the front entrance of the sukka, and one of the side walls extends together with the roofing. Lest you say that this extension does not have the minimum requisite size for the fitness of a sukka, in terms of its area and number of walls, therefore, Ulla teaches us that it is fit because it is considered an extension of the sukka.

Rabba bar bar Ḥana said that Rabbi Yoḥanan said: The Tosefta was needed only to teach the case of a sukka where in its majority its shade exceeds its sunlight, and in its minority its sunlight exceeds its shade. Lest you say that since the extension lacks this basic requirement of a sukka, it is treated as if it were not there at all, and consequently the entire sukka should be rendered unfit due to that little area, therefore, Ulla teaches us that the entire area is one fit sukka. The Gemara asks: According to that understanding of the Tosefta, what is the meaning of: Waste that extends from the sukka? It means that the roofing extends beyond the halakhic parameters for fitness of a sukka. It does not refer to a physical extension of the sukka.

Rabbi Oshaya said: This Tosefta was needed only to teach the case of unfit roofing that measures less than three handbreadths in a small sukka. And what is the meaning of: Waste that extends from the sukka? It means that the roofing extends beyond the halakhic status of a fit sukka; it is not referring to a physical extension of the sukka. Nevertheless, it does not render the entire sukka unfit.

Rav Hoshaya strongly objects to this: What is the novel element in this Tosefta? Let the status of unfit roofing be only as strict as the status of empty space. And does space measuring less than three handbreadths in a small sukka render the entire sukka unfit? If less than three handbreadths of space, which has a stringent measure for rendering the sukka unfit, does not render the sukka unfit, clearly the same measure of unfit roofing does not render the sukka unfit.

Rabbi Abba said to him: There is a distinction between unfit roofing and empty space. This unfit roofing combines with the fit roofing to compose the requisite measure. And one may even sleep beneath it, since the unfit roofing is nullified by the majority of fit roofing and completely incorporated into it. However, that space, although it too combines with the fit roofing to comprise the requisite measure of the sukka, one may not sleep beneath it, as it is not transformed into fit roofing. Therefore, there is a novel element in the explanation of Rabbi Hoshaya as well.

The Gemara questions this contention. Is there any item that combines with other items to engender fitness, but the item itself is not fit? Rabbi Yitzḥak ben Elyashiv said: Yes, that model exists in other areas of halakha as well.