Talmud - Sukkah 17b סוכה י״ז ב׳

the status of the sukka is determined on the basis of whether it is the requisite measure or it is not the requisite measure. In other words, the difference between unfit roofing that is four cubits and unfit roofing that is less is a unique halakha, completely unrelated to the principle of curved wall. Similarly, it is a unique halakha that three handbreadths of space in a roof render a sukka unfit. In this case, there is not the requisite measure according to either halakha; and since their measures are not equal to each other, they do not combine to render the sukka unfit. The sukka is rendered unfit only when the measure of unfit roofing reaches four cubits.

However, according to you, who say that the measure of four handbreadths for unfit roofing is due to the distance between the wall and the fit roofing, which renders the sukka unfit, what is the difference to me if it was distanced due to unfit roofing, and what is the difference to me if it was distanced due to a combination of unfit roofing and space? In either case, the distance between the roofing and the wall should prevent connecting the roofing to the wall. This concludes Rabba’s account of his exchange with the Sages of the school of Rav.

Abaye said to Rabba: And according to the Master, too, although their measures are not equal in a large sukka, which is larger than four cubits, in a small sukka aren’t their measures equal? In a minimally sized sukka, seven by seven handbreadths, three handbreadths of unfit roofing must render the sukka unfit. If the measure of fitness were to remain up to four handbreadths, that would mean that a sukka with a majority of unfit roofing is fit, which is unreasonable. Therefore, Rabba’s contention that the measures of unfit roofing and space are totally different is not precise.

Rabba said to him: There, in the case of the minimally-sized sukka, the fact that the sukka is unfit is not due to the fact that their measures are equal. Rather, it is due to the fact that in a case where the unfit roofing is three handbreadths, the sukka lacks the minimum required measure of fit roofing. In other words, it is not the amount of unfit roofing that creates the problem; rather, it is that the fit area of the sukka is too small.

Rabba maintains that since the two requisite measures of unfitness are not equal, they do not join together. The Gemara asks: And anywhere that their measures are not equal, do they not combine to constitute the requisite measure? But didn’t we learn in the mishna: The garment must be at least three by three handbreadths in order to become a primary source of ritual impurity by means of ritual impurity imparted by treading of a zav; and the sackcloth made from goats’ hair must be at least four by four handbreadths; and the animal hide must be five by five; and a mat must be six by six?

And a baraita is taught concerning the mishna: The garment and the sackcloth, the sackcloth and the hide, and the hide and the mat join together with one another. If one attaches a piece of material that has a smaller, more stringent measure for ritual impurity to a piece of material that has a larger, more lenient measure, the combined cloth is susceptible to contract ritual impurity if together they compose the larger measure. Apparently, two items whose measures are not equal combine to compose the more lenient measure.

The Gemara rejects this. There, it is as the reason is taught that Rabbi Shimon said: What is the reason that these different fabrics combine? They combine since all the component materials are fit to become ritually impure through the ritual impurity imparted to a seat upon which a zav sits, as they can each be used to patch a saddle or saddlecloth. Since they are all suitable for the same use, they join together with regard to the halakhot of ritual impurity. As we learned in a mishna: In the case of one who trims and processes a piece of any of the above-mentioned materials measuring one handbreadth by one handbreadth, that piece is capable of becoming ritually impure. There is a certain halakha for which each of the different materials has the same measure; they therefore join together in other areas as well.

The Gemara asks: For what use is a cloth that is one handbreadth by one handbreadth fit? After all, a rag that has no use does not contract ritual impurity. Rabbi Shimon ben Lakish said in the name of Rabbi Yannai: Since it is suitable for use as a patch on a donkey’s saddlecloth, it is capable of contracting ritual impurity. This ends the discussion of the exchange between Rabba and the Sages of the school of Rav.

The Gemara notes: In Sura, they stated this halakha in that language cited above. In Neharde’a, however, they taught it as follows: Rav Yehuda said that Shmuel said: Unfit roofing in the center of the sukka renders the sukka unfit with a measure of four handbreadths of unfit roofing. Along the side of the sukka, it renders the sukka unfit with a measure of four cubits of unfit roofing. And Rav said: Both along the side and in the center, it renders the sukka unfit with a measure of four cubits of unfit roofing.

We learned in a mishna: If one placed a board that is four handbreadths wide atop the sukka, the sukka is fit. And the Gemara asks: Granted, according to Rav, who said that both along the side and in the center, a sukka is rendered unfit with a measure of four cubits of unfit roofing, it is due to that reason that the sukka is fit. However, according to Shmuel, who said that in the center of the sukka, the sukka is rendered unfit with a measure of four handbreadths of unfit roofing, why is the sukka fit? The Gemara answers: With what are we dealing here? It is with a case where he placed the beam along the side; but had he placed it in the center, then according to Shmuel the sukka would indeed be unfit.

The Gemara cites a proof with regard to Rav’s opinion. Come and hear: Two sheets placed over the roofing of the sukka join together to render the sukka unfit. However, two boards placed on the sukka do not combine to render the sukka unfit. Rabbi Meir says: Even boards have the same legal status as sheets, and they combine to render the sukka unfit.

The Gemara clarifies: Granted, according to that version from Neharde’a that Rav said: Both along the side and in the center, a sukka is rendered unfit with a measure of four cubits of unfit roofing, what is the meaning of join together? It means that the two unfit objects join together to comprise four cubits. However, according to this version from Sura, in which Rav said: A sukka is rendered unfit with a measure of four handbreadths of unfit roofing in the center, what are the circumstances? If each of the boards has four handbreadths in its width, why must they join together to render the sukka unfit? If each board is four handbreadths wide, each is capable of rendering the sukka unfit on its own, and if each of the boards does not have four handbreadths in its width, why would Rabbi Meir prohibit their use; they are merely reeds?

The Gemara answers: Actually, it is a case where each of the boards has four handbreadths in its width, and what is the meaning of join together? It means they join together to constitute four cubits along the side. This understanding fits both versions of Rav’s opinion.

Come and hear proof from another baraita: If one roofed the entire sukka with cedar beams that have four handbreadths in their width, everyone agrees that the sukka is unfit. If they do not have four handbreadths in their width, Rabbi Meir deems the sukka unfit and Rabbi Yehuda deems it fit.

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

Succah 17b examines how invalid roofing measures and roof gaps affect a sukkah's validity, debating whether these distinct halakhic thresholds combine.