Sukkah 19B

טיט הנרוק יוכיח, שמצטרף לארבעים סאה, והטובל בו ⁠— לא עלתה לו טבילה.

The case of mortar that is liquid and can be poured proves that there are situations where items that themselves are unfit render other items fit, as, on the one hand, it combines with water to complete the requisite measure of 40 se’a to render a mikveh fit to purify. But, on the other hand, one who immerses in a bath filled only with mortar, the immersion does not fulfill his obligation.

מתני׳ העושה סוכתו כמין צריף, או שסמכה לכותל ⁠— רבי אליעזר פוסל מפני שאין לה גג, וחכמים מכשירין.

Mishnah: One who establishes his sukka like a type of circular hut, with no roof whose walls slope down from the center or who rested the sukka against the wall, by taking long branches and placing one end on the ground and leaning the other end against the wall to establish a structure with no roof, R' Eliezer deems it unfit because it does not have a roof, and the Rabbis deem it fit; as, in their opinion, the roof and the walls may be a single entity, indistinguishable from each other.

גמ׳ תנא: מודה רבי אליעזר שאם הגביהה מן הקרקע טפח, או שהפליגה מן הכותל טפח ⁠— שהיא כשרה.

Talmud: It was taught in a baraita: R' Eliezer concedes that if one lifted one of these types of sukkot off the ground at least one handbreadth, thereby creating a vertical wall, or if one distanced the sukka resting against the wall one handbreadth from the wall, the sukka is fit. In these cases, the difference between the wall and the roof is conspicuous.

מאי טעמייהו דרבנן? שיפועי אהלים כאהלים דמו.

The Talmud asks: What is the rationale for the opinion of the Rabbis, who deem a sukka fit even where it is an inclined roof rather than a flat one? The Talmud answers: In their opinion, the legal status of the incline of a tent is like that of a tent. As long as it provides shelter, there is no need for a distinct, conspicuous roof for it to be a fit sukka.