סיכך על גבי מבוי שיש לו לחי כשרה
If one placed roofing over an alleyway that has a side post, it is fit for use as a sukka.
ואמר רבא סיכך על גבי פסי ביראות כשרה
And similarly, Rava said: If one placed roofing over upright boards surrounding wells, it is fit for use as a sukka. A well is usually at least four handbreadths wide and ten handbreadths deep. Therefore, it is considered a private domain, and it is prohibited to draw water from it on Shabbat, as that would constitute a violation of the prohibition to carry from a private domain into a public one. In order to permit drawing water from the well, the surrounding area must be partitioned off and rendered a private domain. For the benefit of Festival pilgrims, the Sages instituted a special leniency that full-fledged partitions need not be constructed around the well for this purpose. Rather, it is sufficient if there are four double posts at the four corners of the area surrounding the well. Since these symbolic barriers are considered partitions for the halakhot of Shabbat, they are considered partitions for the halakhot of sukka on Shabbat as well.
וצריכא דאי אשמעינן מבוי משום דאיכא שתי דפנות מעלייתא אבל גבי פסי ביראות דליכא שתי דפנות מעלייתא אימא לא
The Gemara notes: And it is necessary for Rava to state the halakha in each of the two similar cases, as if he had taught us only that the sukka is fit in the case of the alleyway, one could say that it is due to the fact that there are two full-fledged walls; however, in the case of upright boards surrounding wells, where there are not two full-fledged walls and most of the area is breached, say no, it is not considered a fit sukka.
ואי אשמעינן פסי ביראות משום דאיכא שם ארבע דפנות אבל סיכך על גבי מבוי דליכא שם ארבע דפנות אימא לא
And if he had taught us only the case of upright boards surrounding wells, one could say that it is due to the fact that in that case it is in the category of a sukka with four, albeit virtual, walls; however, in the case where one placed roofing over an alleyway, where it is not in the category of a sukka with four walls, say no, it is not considered a fit sukka.
ואי אשמעינן הני תרתי מחמירתא לקילתא אבל מקילתא לחמירתא אימא לא צריכא:
And if he had taught us only these two cases, to teach that a partition with regard to the halakhot of Shabbat is a partition with regard to the halakhot of sukka, one could say that it is due to the fact that one can derive a halakha from a stringency, the halakhot of Shabbat, to a leniency, the halakhot of sukka; however, to derive a halakha from a leniency to a stringency, say no. Therefore, it is necessary to teach the third halakha with regard to a sukka consisting of two walls in the standard sense and a third wall measuring a handbreadth: Since the third wall is considered a wall with regard to the halakhot of sukka, a leniency, it is considered a wall with regard to the halakhot of Shabbat, a stringency.
ושחמתה מרובה מצלתה פסולה:
§ The mishna continues: And a sukka whose sunlight, i.e., the sunlight that passes through the roofing, is greater than its shade, is unfit.
ת"ר חמתה מחמת סיכוך ולא מחמת דפנות רבי יאשיה אומר אף מחמת דפנות
The Sages taught in a baraita that in the statement: Whose sunlight is greater than its shade,the reference is to sunlight that passes through due to sparse roofing, and not to the sunlight entering due to gaps in the walls. It is possible for a sukka to have more sunlight than shade due to sunlight passing through the sides and not the roofing, in which case the sukka is fit. Rabbi Yoshiya says: If the sunlight exceeds the shade the sukka is unfit, even if the sunlight is due to gaps in the walls.
אמר רב יימר בר שלמיה משמיה דאביי מ"ט דרבי יאשיה דכתיב (שמות מ, ג) וסכות על הארון את הפרוכת פרוכת מחיצה וקא קרייה רחמנא סככה אלמא מחיצה כסכך בעינן
Rav Yeimar bar Shelemya said in the name of Abaye: What is the rationale for the statement of Rabbi Yoshiya? It is as it is written: “And you shall screen [vesakkota] the Ark with the curtain” (Exodus 40:3). The curtain is a partition and not a covering over the Ark, and nevertheless, the Merciful One calls it roofing [sekhakha]. Apparently, we require the purpose of a partition to be similar to the purpose of roofing; just as the roofing must be mostly impermeable by sunlight, so must the partition.
ורבנן ההוא דניכוף ביה פורתא דמחזי כסכך
And how do the Rabbis, who disagree with Rabbi Yoshiya, interpret the term: And you shall screen [vesakkota]? That term teaches that we should bend the top of the curtain a bit so that it appears as roofing over the Ark.
אמר אביי רבי ור' יאשיה ורבי יהודה ורבי שמעון ורבן גמליאל ובית שמאי ורבי אליעזר ואחרים כולהו סבירא להו סוכה דירת קבע בעינן
Abaye said: Rabbi Yehuda HaNasi, and Rabbi Yoshiya, and Rabbi Yehuda, and Rabbi Shimon, and Rabban Gamliel, and Beit Shammai, and Rabbi Eliezer, and Aḥerim all hold that we require the sukka to be sturdy and fit for dwelling like a permanent residence.
רבי דתניא רבי אומר כל סוכה שאין בה ארבע אמות על ד' אמות פסולה
Abaye cites the relevant statements of the tanna’im listed above. Rabbi Yehuda HaNasi states this opinion, as it is taught in a baraita that Rabbi Yehuda HaNasi says: Any sukka that does not have an area of four cubits by four cubits is unfit. These are the dimensions of a permanent residence.
רבי יאשיה הא דאמרן
The fact that Rabbi Yoshiya holds that a sukka must be a permanent residence can be seen from that which we stated, that the walls must also be impermeable by sunlight like the walls of a permanent residence.
רבי יהודה דתנן סוכה שהיא גבוהה למעלה מכ' אמה פסולה רבי יהודה מכשיר
Rabbi Yehuda also holds that a sukka must be a permanent residence, as we learned in the mishna: A sukka that is more than twenty cubits high is unfit; Rabbi Yehuda deems it fit. As explained above, in constructing a sukka more than twenty cubits high, one cannot render his residence a temporary residence; rather, he must construct a sturdy permanent residence.
ור' שמעון דתניא ב' כהלכתן וג' אפילו טפח רבי שמעון אומר ג' כהלכתן וד' אפילו טפח
Rabbi Shimon agrees, as it is taught in a baraita: The dimensions of a sukka are two walls in the standard sense, and a third wall that measures even a handbreadth; Rabbi Shimon says: Three of the walls must be walls in the standard sense, and a fourth wall is required that measures even a handbreadth. Apparently, a sukka must be surrounded on four sides like a permanent residence.
רבן גמליאל דתניא העושה סוכתו בראש העגלה או בראש הספינה רבן גמליאל פוסל ור"ע מכשיר
Rabban Gamliel holds that a sukka must be a permanent residence, as it is taught in a baraita: In the case of one who establishes his sukka atop a wagon or atop a boat, Rabban Gamliel deems it unfit; a mobile structure is not a permanent residence. Rabbi Akiva deems it fit. Apparently, Rabban Gamliel requires that a sukka be a permanent residence.
בית שמאי דתנן מי שהיה ראשו ורובו בסוכה ושולחנו בתוך הבית בית שמאי פוסלין ובית הלל מכשירין
Beit Shammai agree, as we learned in a mishna: In the case of one whose head and most of his body were in the sukka and his table was in the house, Beit Shammai deem the sukka unfit, since a small sukka is unfit for use and one cannot fulfill the mitzva of sukka with it. And Beit Hillel deem it fit. Apparently, Beit Shammai require that the sukka be similar to a permanent structure.
רבי אליעזר דתנן העושה סוכתו כמין צריף או שסמכה לכותל רבי אליעזר פוסל לפי שאין לה גג וחכמים מכשירין
Rabbi Eliezer holds that a sukka must be a permanent residence, as we learned in a mishna: In the case of one who establishes his sukka like a type of circular hut whose walls slope down from the center and has no roof, or one who rested the sukka against the wall, taking long branches and placing one end on the ground and leaning the other end against the wall, establishing a structure with no roof, Rabbi Eliezer deems it unfit because it does not have a roof, and the Rabbis deem it fit. A permanent residence has a roof.
אחרים דתניא אחרים אומרים סוכה העשויה כשובך פסולה לפי שאין לה זויות
Aḥerim agree, as it is taught in a baraita that Aḥerim say: A sukka built in a circular shape like a dovecote is unfit, because it does not have corners, and a permanent residence is one with corners.
אמר ר' יוחנן סוכה העשויה ככבשן אם יש בהקיפה כדי לישב בה כ"ד בני אדם כשרה ואם לאו פסולה
§ Rabbi Yoḥanan said: With regard to a sukka that is shaped like a furnace and is completely round, if its circumference has sufficient space for twenty-four people to sit in it, it is fit, and if not, it is unfit.
כמאן כרבי דאמר כל סוכה שאין בה ארבע אמות על ארבע אמות פסולה
The Gemara asks: In accordance with whose opinion did Rabbi Yoḥanan rule that the sukka must be so expansive? The Gemara answers: It is undoubtedly in accordance with the opinion of Rabbi Yehuda HaNasi, who said: Any sukka that does not have an area of four cubits by four cubits is unfit. Since he requires the sukka with the largest minimum dimensions, Rabbi Yoḥanan must hold in accordance with his opinion.
מכדי גברא באמתא יתיב כל שיש בהקיפו שלשה טפחים יש בו רוחב טפח בתריסר סגי
However, even if he holds in accordance with the opinion of Rabbi Yehuda HaNasi, the question arises: Now, since when a person sits, he occupies one cubit of space, the circumference required by Rabbi Yoḥanan for the sukka is twenty-four cubits. However, mathematically, for every three handbreadths circumference in a circle, there is a diameter of approximately one handbreadth. Consequently, rather than requiring a sukka that holds twenty-four people, a sukka that holds merely twelve people should suffice, since a sukka with a circumference of twelve cubits has a diameter of approximately four. In that case, why does Rabbi Yoḥanan require the sukka to have double the necessary circumference?