MAY ONE CROSS THE RESHUS IN WHICH THE 2000 AMOS END?
Defense (Rava): Both of these are learned from a Mishnah!
(Mishnah): [If a big city and a small city are less than 2000 Amos apart,] people of the big city may traverse all of the small city [without deducting from their 2000 Amos,] but people of the small city may not traverse all of the big city.
Question: What is the reason?
Answer: The 2000 Amos of someone in the big city extend past the small city, but the 2000 Amos of someone in the small city end in the middle of the big city.
R. Idi questioned the law, for his text in the Mishnah said in both cases that people of' one city traverse all of the other city;
He established it to discuss one who placed an Eruv in the other city. The Mishnah does not discuss one who measures 2000 Amos outside his city [through counting 2000 steps].
Question: The Seifa discusses this!
(Mishnah): We learned that one who measures his Techum gets 2000 Amos. This is even if they end at a cave [he may not enter it].
Answer: The Mishnah does not discuss one whose 2000 Amos end at the end of a city.
(Rav Nachman): Both texts of the Mishnah are reasonable:
The opinion that the text permits in both cases says that the Mishnah discusses one who placed an Eruv in the other city;
The opinion that the text does not permit people of the small city to traverse all of the big city says that the Mishnah discusses one who measures. It is abbreviated. It means as follows;
People of the big city may traverse all of the small city, but people of the small city may not traverse all of the big city.
This refers to one who measures. However, if someone in either city placed an Eruv in the other city, he may traverse all of it and 2000 Amos outside of it.
A CITY NEXT TO A RIVER
(Rav Yosef citing Rav Huna): If a city is at the edge of a river:
If there is a Dakah that is Arba'ah (four; the masculine form connotes Tefachim) along the border between it and the river, we measure 2000 Amos from the edge of the river. If not, everyone measures from the opening of his house. (Since people are afraid to get close to it, it is not so settled, so the law of hut dwellers applies.)
Abaye: You taught us that the Dakah must be four Amos!
Question: Why is this different from all other Dakos? Their Shi'ur is four Tefachim!
Answer: Here, one is afraid [lest he fall into the river]. Normally, one is not afraid.
Support (Rav Yosef, for himself - Beraisa): Rebbi permitted people of Geder (a city) to descend to Chamsan [on Shabbos], but not vice-versa.
Suggestion: [This is because they were on opposite sides of a river, and] there was a wall between Geder and the river, but not between Chamsan and the river!
Rejection #1 (Rav Dimi): No. People of Geder used to hide in ambush to kill people of Chamsan. Rebbi did not permit Bnei Geder to descend to Chamsan. Rather, he enacted [that Bnei Chamsan not descend to Geder].
Question: Why was the enactment only for Shabbos?
Answer: People often get drunk on Shabbos.
Question: Bnei Geder could kill Bnei Chamsan when they go there!
Answer: [They are timid there.] A dog outside its city will not bark for seven years.
Question: If so, perhaps Bnei Chamsan will kill Bnei Geder [to take vengeance]!
Answer: They are not so timid there.
Version #1 (Rav Kahana) Rejection #2 (Rav Safra): No. Chamsan was shaped like a bow. (The ends were more than 4000 Amos apart, so we measure from the bow. Geder was in the direction of the Yeser. Chamsan was within the Techum of Geder, but not vice-versa.)
Rejection #3 (Rav Dimi bar Chinena): Geder was a big city and Chamsan was a small city. (The coming Mishnah permits people of the big city to traverse all of the small city, but not vice-versa.)
Version #2: Rav Tivyomi taught these rejections in the name of Rav Safra and Rav Dimi, but he was unsure who said which.
CAN ONE CROSS THE RESHUS IN WHICH HIS 2000 AMOS END?
(Mishnah): People of the big city may traverse all of the small city. People of the small city may (the text of some Amora'im says 'not') traverse all of the big city.
If someone in the big city placed an Eruv in the small city, or vice-versa, he may traverse all of it and 2000 Amos outside of it;
R. Akiva says, he has only 2000 Amos from his Eruv.
R. Akiva: Don't you agree that one who was Me'arev in a cave has only 2000 Amos from the Eruv?!
Chachamim: This is only if no one dwells in the cave. If people dwell there, he may traverse all of it and 2000 Amos outside.
The law of a cave is more lenient than on top of it. (No one dwells on top, so one has only 2000 Amos from the Eruv.)
We learned that one who measures his Techum gets 2000 Amos. Even if they end at a cave, he may not enter it. (The 2000 Amos were in addition to his four Amos, so we do not give him any more.)
(Gemara - Rav Yehudah): If one was Shoves in a desolate city (the walls are intact, but no one dwells there), he may traverse all of it and 2000 Amos outside.
If one placed an Eruv in a desolate city, he has only 2000 Amos from the Eruv.
(R. Elazar): In either case, he may traverse all of it and 2000 Amos outside.
Question (Mishnah - R. Akiva): Don't you agree that one who was Me'arev in a cave has only 2000 Amos from the Eruv?!
Chachamim: This is only if no one dwells in the cave...
Inference: If no one dwells there, all agree that he has only 2000 Amos from the Eruv!
Answer: 'If no one dwells there' means that it is not proper to dwell there.
Question (Beraisa): If one was Shoves in a city, even if it is as big as Antiyuchya, or in a cave, even if it is as big as Tzidkiyahu's cave (from which he left Yerushalayim), he may traverse all of it and 2000 Amos outside.
Inferences: It teaches about a city and a cave. Surely, just like the cave is desolate, also the city;
It teaches about one who was Shoves, but not if he placed an Eruv. (Then, he gets only 2000 Amos.)
Question: Who is the Tana of the Beraisa?
It is not R. Akiva. He holds that whether or not a city is desolate, one who places an Eruv has only 2000 Amos!
Answer: It is Chachamim, and it allows 2000 outside the city only if he was Shoves, but not if he placed an Eruv!
Answer: No, it teaches about a cave that is like a city. It is inhabited. It is like R. Akiva, who says that he has only 2000 Amos;
He agrees about one who is Shoves. (He gets 2000 Amos outside the city.)
Question: The Beraisa discusses Tzidkiyahu's cave [which was desolate]!
Answer: It discusses a cave as big as Tzidkiyahu's, but it is inhabited, unlike Tzidkiyahu's cave.
Mar Yehudah saw people of Mevarkesa place Eruvin in the Beis ha'Keneses of Bei Avugar.
Mar Yehudah: Put it deeper into the city [in the direction you wish to walk. Since you get 2000 Amos from the Eruv], this will permit you to go further!
Rava: You oppose Chachamim! No one is concerned for R. Akiva's opinion!
DOES A NOCHRI'S RESHUS FORBID?
(Mishnah): If a Yisrael lives in a Chatzer with a Nochri (i.e. their houses open to the same Chatzer), or with one who does not acknowledge [the enactment of] Eruv (i.e. a Kusi), the Nochri [or Kusi] forbids the Yisrael [to transfer between his house and the Chatzer, unless he rents the Nochri's Reshus for Shabbos];
R. Eliezer ben Yakov says, he does not forbid unless [at least] two Yisraelim live in [different houses open to] the Chatzer and forbid each other [from carrying without an Eruv. An Eruv is invalid unless they rent the Nochri's Reshus.]
R. Gamliel says, a case occurred in which a Tzeduki lived with us in a Mavoy in Yerushalayim. (Tzedukim do not heed Divrei Chachamim.) My father told us 'quickly take Kelim into the Mavoy before he does and forbids you!' (This will be explained.)
R. Yehudah says, he told them 'do your needs in the Mavoy [before Shabbos], before he will take out into the Mavoy and forbid you.'