THE CHACHAMIM'S OPINION ABOUT THE THREE CHATZEROS
Version #1 (our text, Rashi) (Rav): This is R. Shimon's opinion. Chachamim say that [whether the Eruvin were placed in the middle Chatzer or the outer Chatzeros,] one Reshus (the middle Chatzer) can be used by two Reshuyos (a Kli that was Shoves in either outer Chatzer may be used there. We are not concerned lest someone from the other outer Chatzer use it, for they were not Me'arev together), but two Reshuyos (the outer Chatzeros) may not be used by one Reshus. (The middle Chatzer may not use even their own Kelim there, lest they use Kelim of the outer Chatzer.)
Version #2 (most Rishonim) (Rav): This is R. Shimon's opinion. Chachamim say that one Reshus may use two (the middle Chatzer may use its Kelim in the outer Chatzeros. They will not take Kelim of an outer Chatzer to the other, for people recognize their own Kelim), but two Reshuyos may not use one (an outer Chatzer may not use its Kelim in the middle Chatzer. If everyone would be permitted there, an outer Chatzer might come to use Kelim of the other outer Chatzer). (end of Version #2)
(Shmuel): Chachamim do not allow even this. Only R. Shimon does. Chachamim forbid all [transfer between the] three Chatzeros.
Support (for Shmuel - Beraisa - R. Shimon): This is like three Chatzeros open to each other and open to Reshus ha'Rabim:
If the outer Chatzeros were Me'arev with the middle Chatzer, each may bring food from its house to the middle, eat, and return its leftovers to its house;
Chachamim say, all three of them are forbidden [with each other].
This is like Shmuel taught elsewhere;
(Shmuel): If a Chatzer between two Mavo'os was Me'arev with both of them, it is forbidden with both of them;
If it was not Me'arev with both of them, it forbids both of them;
If it normally used [only] one of them, it forbids only that one.
(Rabah bar Rav Huna): If it was Me'arev with the one it normally uses, this permits the other one.
(Rabah bar Rav Huna): If the one it normally uses was Me'arev by itself, and the other Mavoy and this Chatzer were not Me'arev, we force this Chatzer to use that Mavoy [lest it forbid the one that was Me'arev]. In such a case, Kofin Al Midas Sedom. (We force one to allow another to benefit, if he himself will not lose.)
AN ERUV UNITES
(Rav Yehudah): If someone is strict about his Eruv (unwilling to let a member of the Chatzer take it), it is invalid;
It is called Eruv. (This connotes a [friendly] union.)
(R. Chanina): It is an Eruv, just he is called stingy.
(Rav Yehudah): If one divided his Eruv (put it in two Kelim), it is invalid. (It is not a union!)
Suggestion: This is like Beis Shamai!
(Beraisa - Beis Shamai): If five people gave for the Eruv and it was put in two Kelim, it is invalid;
Beis Hillel are Machshir.
Rejection: It is even like Beis Hillel. They are Machshir only when the Kli was full, and he was forced to use another Kli. They agree that if one deliberately divides it among two Kelim that it is invalid.
Question: Why must Rav Yehudah teach both of these?
Answer: He must teach both. From the first, we would only know that if one is strict, his Eruv is invalid. We would not knew about one who divided it;
From the second, we would only know that a divided Eruv is invalid. We would not know about one who is strict.
Question (R. Aba): Surely, Shmuel is Machshir a divided Eruv. He taught that the host (in whose house the Eruv is put) need not contribute to the Eruv!
Suggestion: Even though the host's own bread is in a different Kli, it is considered to be part of the Eruv. The same applies if the Eruv itself is in two Kelim!
Answer: No, the Eruv is valid even if the host has no bread;
Through Eruv, it is considered as if everyone dwells in this house. The host truly dwells there!
(Shmuel): Eruv works through acquisition. (The host makes them partners in his house.)
Question: If so, people should give money for an Eruv!
Answer: Not everyone has money on Erev Shabbos (but everyone has bread at this time).
Question: If someone gave money, it should be a valid Eruv!
Answer: We decree that it is invalid, lest people think that an Eruv must be through money, and when people lack money, they will not Me'arev with bread, and the law of Eruv will be forgotten.
(Rabah): Eruv works through Dirah. (It is as if everyone lives in the host's house.)
Question: What is the difference between these explanations?
Answer: They argue about whether or not one may transfer ownership of the Eruv through a Kli (Chalifin), whether or not the Eruv must be worth a Perutah, and whether or not a minor can be Me'arev. (Chalifin is valid for acquisition, but less than a Perutah and a child are not. For Dirah, it suffices that [the proper quantity of] food is there. Chalifin does not suffice.)
Question (Abaye): A Beraisa is difficult for both opinions!
(Beraisa): If five members of a Chatzer were Me'arev, one of them can take the Eruv elsewhere [to join with another Chatzer].
(Why does this help for the entire Chatzer? Only the one who took it acquired. Only he has Dirah in the other Chatzer!
Answer (Rabah, for himself and Shmuel): The one who took it was a Shali'ach on behalf of his entire Chatzer.
(Rabah): The Halachah follows R. Shimon.
DECLARING SHEVISAH FROM A DISTANCE
(Mishnah - R. Chanina ben Antigonus): If one was traveling and it was [getting] dark for him [on Erev Shabbos], and he saw a fence or tree and said 'my Shevisah is under it', his words have no effect;
If he said 'my Shevisah is at the trunk', he may walk 2000 Amos to the tree, and another 2000 Amos from the trunk to his house, 4000 Amos in all after dark.
If he did not see a fence or tree, or did not know the Halachah, and said 'my Shevisah is where I am', he gets 2000 Amos in every direction, i.e. a circle [of radius 2000];
Chachamim say, he gets a square [of side 4000], he gains the corners. (He may walk 2000 Amos north [or south], and additionally 2000 east [or west].)
This is like it was taught, that an Oni [who lacks bread, like this traveler] can be Me'arev through walking;
R. Meir says, only an Oni can do so;
R. Yehudah says, the same applies to an Ashir;
An Eruv with bread is a leniency for Ashirim, so they need not walk.
(Gemara) Question: What is the meaning of 'his words have no effect'?
Answer #1 (Rav): His words have no effect at all. He may not even go to the tree;
Answer #2 (Shmuel): His words do not permit him to return home, but he may go to the tree. He is in Chamar Gamal with respect to the entire area under the tree (his Shevisah is somewhere in this area. We do not know exactly where it is. His house is more than 2000 Amos from part of the tree):
If he wants to go north, he gets 2000 Amos from the [part of this area furthest] south. If he wants to go south, we measure from the north.