The Talmud brings two other opinions that concur with Rav from above.
There is now a third opinion about where to put the third wall. The third wall should be a “loose” handbreadth which is like a handbreadth with expanded fingers. He then places that handbreadth within three handbreadths of one of the existing walls. Less than three handbreadths is considered to be halakhically insignificant. This way he now has a four handbreadth wall. Four handbreadths is a majority of the minimum size for a wall—seven handbreadths. So in this way he has a wall that is more than half of what it needs to be.
There is another opinion concerning the sukkah built like an alleyway. According to this opinion he must make a wall that is at least a little bit more than four handbreadths. He places this strip within three handbreadths of one of the walls, which means that it counts as being joined to the wall. That allows there to be a 7 handbreadth wall, fulfilling the minimum requirement.
One can make a sukkah with two parallel walls. The third wall can be placed in the middle between the two, wherever he so wishes.
The Talmud now notes that R. Simon (or R. Joshua ben Levi) seems to contradict himself. Above he said that it was sufficient to have one loose handbreadth, but here he said that the strip must actually be four handbreadths.
In the other case there are already two walls forming a right angle. These are basically 2/3 of a valid sukkah. Since they are already valid, we only need one more handbreadth wall to create a proper sukkah. But in this case where the two walls are not connected, we need a four handbreadth wall to create a proper sukkah.
Today’s section deals with a statement by Rava that for the sukkah to be valid it needs to have “the form of a doorway.”
Rava rules that for the sukkah with this third wall that is only a handbreadth to be valid it must also have the “form of a doorway.” Rashi explains that this is accomplished by dividing a handbreath into halves—each half is placed on opposite sides and a pole is put across them to create the form of a doorway.
Above in the previous section R. Simon had said that the handbreadth wall must be a “loose handbreadth” placed within three handbreadths of the other wall. In this way he could fictionally create a full seven handbreadth wall. According to this version of Rava’s statement if there is the form of a doorway on the third wall, he doesn’t need the handbreadth wall to be within three handbreadths of the other wall. Note that according to this version, Rava offers a leniency.
According to this version Rava supplements R. Simon’s requirement that this type of sukkah, one whose third wall is a handbreadth. Rava says that even after he puts the handbreadth wall up and places it within three handbreadths of the other wall, he still needs to make the form of a doorway. According to this version, Rava is a stringency upon R. Simon’s ruling.
We now have a story related to the above discussion. R. Ashi, a late Babylonian amora sees R. Kahana his teacher, building a sukkah where he made the third wall a loose handbreadth, as R. Simon said in yesterday’s section. R. Kahana was also making the form of a doorway. This seems to accord with the third of Rava’s statements, that this sukkah also requires a doorway.
R. Ashi now asks R. Kahana why R. Kahana doesn’t hold like the more lenient of Rava’s opinion, according to which if he has the form of a doorway, he doesn’t need the “loose handbreadth.”
R. Kahana answers that he follows the other statement of Rava, the more stringent one. This type of sukkah requires both the loose handbreadth placed within three handbreadths of the other wall and the form of a doorway.
Thus we can see that there was a debate among these late amoraim as to whether Rava ruled stringently (R. Kahana) or leniently (R. Ashi).
This section is based on another statement by Rava concerning the status of a one handbreadth wall on Shabbat.
Rava said: And similarly with regard to the Shabbat. Since [the handbreadth] is regarded as a valid wall of the Sukkah it is also regarded as a valid wall in respect of the Sabbath.
Rava says that since the one handbreadth wall is effective in making the sukkah valid, so too it is effective in allowing one to carry within the walls on Shabbat.
Does this not mean that the law relating to the Shabbat of Sukkot is more [stringent] than that relating to the Sukkah itself, and that we do not apply the rule of ‘since’?
Rava above implied that any time a wall is kosher for use in the sukkah it is also kosher for allowing one to carry on Shabbat. Abbaye however brings a baraita that shows that sometimes the law differs. Both walls cannot have gaps of greater than three handbreadths. But the laws of Shabbat are more stringent in that there must be more wall than empty space.
This means that if we have a sukkah standing on Sukkot whose gaps are greater than the standing portion the sukkah is valid as a sukkah but one could not carry within it. This proves that we don’t say, “since it is valid as a sukkah it is valid to allow carrying on Shabbat.”
Rava now responds, or at least the Talmud responds on his behalf. During Sukkot, if a wall is valid for the purpose of the sukkah, it is valid to allow carrying within the sukkah on the Shabbat of the festival. But during the rest of the year, one would not be able to rely upon such a wall to carry. Strangely, there can be a sukkah in which one could carry on Sukkot, but not during the remainder of the year.
Abbaye now responds against Rava. As a background we need to understand a statement made elsewhere by Rava that if one puts skhakh up on an alleyway that has a post on its end, the sukkah is valid. This post is part of the eruv system and it allows one to carry from the courtyard to the alleyway. So if Rava is correct that a wall that allows one to carry on Shabbat should also be valid as a Sukkah wall, then the sukkah shouldn’t require a third wall that is a full handbreadth. Even the “post” which is less than a handbreadth should be sufficient.
Rava responds that the baraita did not even need to state that. If the lenient case of the sukkah (it’s a positive commandment which are considered more lenient than negative ones) can dictate to the stringent case of Shabbat (whose penalty is the death penalty) that a wall is valid to allow carrying, then all the more so a wall that we allow carrying on Shabbat should be able to dictate what counts as a wall for the issue of Sukkot.