Question (Rav Nachman bar Yitzchak): What was Rav Chisda unsure about?

Did he have enough people [that could leave the Techum to make Mechitzos from the Techum until where Nechemyah was standing, i.e. they were Me'arev in that direction], but he was unsure whether or not the Halachah follows R. Gamliel [who says that Mechitzos permit even one who was not Shoves inside them]?

Or, did he not have enough people [but he had enough to make Mechitzos from where Nechemyah was standing to within two Amos of the Techum], and he was unsure whether or not the Halachah follows R. Eliezer [who permits (52b) one who went two Amos outside the Techum to re-enter]?

Answer (Rava): It was the latter. Surely, he knew that Rav said that the Halachah follows R. Gamliel regarding a Dir, Sahar or boat!

Support: Rav Nachman said '...and he may re-enter';

Surely, this means that they will make Mechitzos up to two Amos outside the Techum, and from there he may enter without Mechitzos!

Question (Rav Nachman bar Yitzchak - Beraisa #1): The following are forbidden due to making a temporary Ohel on Yom Tov, and all the more so they are forbidden on Shabbos:

If the wall [of a Sukah] fell, one may not stand up in its place a person, animal or Kelim;

One may not erect a bed to spread a sheet over it.

Contradiction (Rava - Beraisa #2): Reuven may use Shimon for a wall [for Reuven's Sukah] to permit eating, drinking and sleeping. One may erect a bed to spread a sheet over it to shield a Mes or food from the sun.

Answer #1 (Rava): Beraisa #1 is R. Eliezer, and Beraisa #2 is Chachamim. (Rav Nachman holds like Chachamim);

(Mishnah - R. Eliezer): If a window stopper is tied and hangs [above the ground], one may use it to close a window. If not, one may not;

Chachamim say, in either case one may use it to close.

Rejection: Rabah bar bar Chanah taught that all forbid making a new temporary Ohel on Yom Tov, and all the more so on Shabbos. They argue about adding to an Ohel:

R. Eliezer forbids adding on Yom Tov, and there is no need to say that he forbids on Shabbos;

Chachamim permit adding on Shabbos, and all the more so they permit on Yom Tov.

Answer #2: Beraisa #2 is R. Meir, and Beraisa #1 is R. Yehudah:

(Beraisa - R. Meir): If one made an animal to be a Sukah wall, it is invalid;

R. Yehudah is Machshir.

R. Meir is Posel. Since it is not a Mechitzah, he did nothing, so there is no reason to forbid;

R. Yehudah holds that it is a Mechitzah, therefore he forbids.

Objection #1: Granted, R. Meir disqualifies an animal for a wall [for it might go away]. However, you have no source that he disqualifies a person (he knows that he must stay) or Kelim!

Objection #2 - Question: According to whom does R. Meir Posel?

This is not like R. Eliezer. He forbids even to add [to an Ohel]!

Suggestion: It is like Chachamim.

Rejection: Chachamim permit adding to an Ohel. They do not permit making a new Ohel!

Answer #3: Both Beraisos are like Chachamim. They forbid making the third wall of a Sukah [since this makes it an Ohel]. They permit making the fourth wall [since it was already an Ohel].

Support (Beraisa #1): If the wall fell... (this suggests the third wall, which is Machshir the Sukah).

Question: This answers regarding animals [and Kelim]. How can we answer regarding people? (Beraisa #2 says that a person permits eating and sleeping. It must refer to the third wall!)

Answer: A person can be a Mechitzah only if he is unaware of this.

Question: The people who made Mechitzos for R. Nechemyah (43b) knew about this!

Answer: No, they did not.

Question: Rav Chisda knew about it!

Answer: He was not part of the Mechitzos.

Some gardeners made Mechitzos of people to bring water [from Reshus ha'Rabim to Reshus ha'Yachid. The people understood this.] Shmuel lashed them (the gardeners).

(Shmuel): It is permitted only if they do not know, but not if they know!

Rava had pouches in the street in his city. When Rava returned after teaching Talmidim, a throng followed him. Rava's attendant picked them up (he was within Mechitzos of Talmidim). Another Shabbos the attendant wanted to do so for Rava. He forbade, for this was like knowingly. (Perhaps Talmidim understood by now.)

People used human Mechitzos to bring Levi's straw, Ze'iri's fodder, and water for Rav Simi bar Chiya.

(Mishnah): If one was permitted to leave the Techum (e.g. to testify about the new moon or to save lives) and he found out that the Mitzvah was already done, he has 2000 Amos [from where he was when he found out];

If he was still inside the Techum, it is as if he never left.

Anyone who leaves the Techum to save may return to his place.

(Gemara) Question: What is the meaning of 'if he was still inside the Techum, it is as if he never left'?

Version #1 - Answer #1 (Rabah): If he was still in his Techum, it is as if he never left his house.

Objection: This is obvious!

Answer: One might have thought that once he left, the enactment [that one who left the Techum with permission gets 2000 Amos from where he finds out] applies [even if this extends past his Techum]. The Mishnah teaches that this is not so.

Version #2 - Answer #1 (Rabah): If the Techum (2000 Amos) he receives overlaps his Techum (i.e. he is less than 2000 Amos outside his Techum), it is as if he never left his house (he does not receive a new Techum). (end of Version #2)

Answer #2 (Rav Simi bar Chiya): If the Techum he receives overlaps his Techum, it is as if he never left his Techum (he receives a new Techum without losing his old Techum.

Question: What is the source of their argument?

Answer: Rav Simi holds that overlap of Techumim is significant. Rabah holds that it is not significant.

Question (Abaye, to Rabah): Surely, you should agree that overlap of Techumim is significant!

If one was Shoves in a cave of 4000 Amos and its roof is less than 4000 (the walls slant inward), he may walk on the entire roof and 2000 Amos outside (in either direction! This is because the Techum he gets when he leaves from the east overlaps the Techum he would get had he left from the west. Therefore they are like one Techum.

Answer (Rabah): There is different, for he was Shoves within those Mechitzos from before Shabbos. I discuss one who left the Mechitzos in which he was Shoves. (Version #1 - he loses his initial Techum. Version #2 - he does not get a new Techum.)