(Rav Yehudah citing Shmuel): If there is a pit [in a Mavoy] between two Chatzeros four Tefachim away from [the wall of] each, each must extend a ledge of any size from its wall in order to draw water from it.

(Rav Yehudah himself): It suffices for each to extend a reed [from its wall].

Abaye: [Surely,] Rav Yehudah learned this from Shmuel! (He was a Talmid of Rav and Shmuel);

It is not from Rav, for Rav holds that one who uses something through the air (it is horizontally four Tefachim away from him) does not forbid another from using it!

Question: (Abaye says that Rav Yehudah learned from Shmuel that some Tikun is required.) From which teaching did he learn? (Surely, if Abaye teaches that Rav Yehudah learned this from Shmuel, he did not hear Rav Yehudah explicitly say this in the name of Shmuel!)

Answer #1: Rav Nachman taught in the name of Shmuel that if a roof borders Reshus ha'Rabim, it is permitted only if there is a fixed ladder. [Normally, the width of Reshus ha'Rabim does not extend to houses on the side, low rocks keep them four Tefachim away. Even so, they forbid due to usage through air!]

Rejection: Perhaps this is like Rav Papa established it. (Rabim rest their hats and turbans on it. This is convenient. We cannot learn from it to regular usage through air.)

Answer #2: Rav Yehudah learns from what he himself said in the name of Shmuel, that when there is a pit between two Chatzeros, each must extend a ledge of any size;

Without the ledge, they forbid each other due to usage through air! (Really, Abaye heard the teaching. Rav Yehudah himself taught a bigger Chidush, that a reed suffices. He learned this from Shmuel. Since any size ledge suffices, it is a mere Heker lest they come to use a joint Reshus without an Eruv, so even a reed suffices.)

Question: From which teaching of Rav do we know that he holds that usage through air does not forbid?

Answer #1: A Mishnah teaches that if two balconies are one above the other, and a Mechitzah was made only for the top one, both are forbidden unless they are Me'arev together;

(Rav Huna citing Rav): This is only if they are close [within four Tefachim of each other horizontally]. If they are four apart, the upper one is permitted, and the lower one is forbidden.

Rejection: Perhaps there, usage through air does not forbid because [of another factor --] the upper balcony's usage is [relatively] convenient and the lower balcony's is inconvenient. The top balcony just lowers, but the lower balcony must throw and lower!

Answer #2: Rav Nachman said in the name of Rav that if there are three ruins [in a row] between two houses, each house may use the ruin adjacent to it through throwing [through a window]. The middle ruin is forbidden [to both of them].

Rav Berona said this in the name of Rav. R. Elazar was skeptical. He went to ask Rav if he indeed said it. Rav said that he did.

R. Elazar: [Since you forbid the middle ruin, this shows that usage through air forbids. If so, you must permit to each house the ruin near it because it is more convenient for it than for the other house.] However, you taught that if one uses through throwing and the other by lowering, both are forbidden [even though lowering is more convenient than throwing]!

Rav: You assume that the ruins are in a line. Really, they are in a triangle [like the picture in the Gemara]. Each is adjacent to the middle ruin. This is not usage through air.

Suggestion (Rav Papa): Shmuel [who forbids due to usage through air] argues with Rav Dimi [even though a Mishnah (76b) supports Rav Dimi]!

(Rav Dimi citing R. Yochanan): If a place [at least three Tefachim tall] is less than four by four [Tefachim, it is Makom Patur], people of Reshus ha'Rabim or Reshus ha'Yachid may unload on it, as long as they do not use it to transfer [from one Reshus to the other. Such a small place is inconvenient, like usage through air!]

Rejection: No, Shmuel agrees about Reshuyos mid'Oraisa (Reshus ha'Yachid and Reshus ha'Rabim);

He argues about Reshuyos mid'Rabanan. He holds that [for them] Chachamim were more stringent about their decrees than about Torah laws.

Question (Ravina): Rav could not have said this ((k), that each house may use the ruin adjacent to it, for the other house does not forbid due to usage through air)!

(Rav): If there are two houses on opposite sides of Reshus ha'Rabim, one may not throw from one to the other;

(Shmuel): It is permitted.

Answer: We established that they discuss when one of the houses is higher than the other. [It is difficult to reach the destination, therefore] Rav forbids lest the object fall in Reshus ha'Rabim and he will come to take it.

(Mishnah): If one put an Eruv in a Beis Sha'ar, Achsadra or porch, it is invalid;

One who lives in one of these [need not give towards the Eruv in the Chatzer, for he] does not forbid.

If one put an Eruv in a cattle pen or storehouse for straw, wood or produce, it is valid;

One who lives in one of these forbids [if he does not give towards the Eruv];

R. Yehudah says, if the owner has Tefisas Yad (rights of usage), the one who dwells there does not forbid.

(Gemara - Rav Yehudah): Any place that [someone living there] does not forbid, if one put Eruv [Chatzeros] there, it is invalid, except for a Beis Sha'ar of an individual;

Any place that is invalid for [putting] an Eruv is valid for Shituf, except for [the open floor of] a Mavoy.

Question: We already learn this from our Mishnah!

(Mishnah): If one put an Eruv in a Beis Sha'ar, Achsadra or porch, it is invalid.

Inference: Shituf is valid in these places!

Answer: He needs to teach about a Beis Sha'ar of an individual and [the open floor of] a Mavoy, which the Mishnah did not teach.

Support (Beraisa): If one put an Eruv in a Beis Sha'ar, porch, Chatzer or Mavoy, it is valid;

Contradiction (Mishnah): It is invalid.

Resolution: We must say that the Beraisa permits Shituf in these places.

Question: Why is the Beraisa Machshir if it was left in a Mavoy? It is not guarded there!

Answer: It should say 'Chatzer in a Mavoy' [and not 'Chatzer or Mavoy'].

Version #1 (Rav Yehudah): If people were eating together and Shabbos came, they can rely on the bread on the table for Eruv;

Version #2 (Rav Yehudah): They rely on it for Shituf.

(Rabah): The versions do not argue. If were eating in a house, they rely on it for Eruv. If were eating in a Chatzer, they rely on it for Shituf.

Support (Abaye - Beraisa): Eruvei Chatzeros are left in the Chatzer, and Shitufei Mavo'os are left in the Mavoy.

Question: An Eruv in the Chatzer is invalid!

(Mishnah): If one put an Eruv in a Beis Sha'ar, Achsadra or porch, it is invalid.

Answer: The Beraisa means 'Eruvei Chatzeros are left in a house in the Chatzer, and Shitufei Mavo'os are left in a Chatzer in the Mavoy.

(Mishnah - R. Yehudah): If the owner has Tefisas Yad, the one who dwells there does not forbid.

Question: What is considered Tefisas Yad?

Answer: It is like the Chatzer of (Bach - ben) Bunyas. (He had many Kelim in houses, and he would let people live in the houses.)