A MECHITZAH IN WATER
(R. Chiya - Beraisa): If a fishing trap is between the Techum of two cities, one must put an iron wall [in the water between the Techumim. If not, one may not take water, even though it is from his Techum].
R. Yosi b'Rebbi Chanina laughed at this.
Question: Why did he laugh?
Suggestion: The Beraisa is stringent like R. Yochanan ben Nuri, and he is lenient like Chachamim.
Rejection: This is no reason to laugh!
Answer #1: A Beraisa teaches that the water from flowing rivers and springs gets the Techum of the one who draws it.
Objection: Perhaps R. Chiya discusses still water!
Answer #2: He requires an iron wall to separate;
Presumably, a wall of sticks is not good because water goes through - water also goes through an iron wall! (He did not require it to reach to the sea floor. Even if it does, some water will pass under it.)
Objection: Perhaps R. Chiya means that one needs a wall impervious to water, and there is no solution!
Answer #3: He laughed because Chachamim are lenient about water [to allow Mechitzos even though water passes above or below], like Rav taught:
Question (R. Tavla): Does a hanging Mechitzah permit carrying in a ruined house?
Answer (Rav): Chachamim gave this leniency only regarding water.
THE FOUR AMOS ONE IS GIVEN TO WALK
(Mishnah - Chachamim): He has only four Amos... [R. Yehudah says, he can go four Amos in any direction he wants].
Question: R. Yehudah does not argue with Chachamim!
Answer (Rava): Chachamim permit four in both directions. R. Yehudah permits four in any direction he chooses.
Support (Beraisa - R. Meir): He is permitted eight by eight [Amos].
(Rava): They argue about where he may walk, but all agree that he may carry only within four Amos.
Question: Where does the Torah allude to these four Amos?
Answer (Beraisa - R. Meir): "Shevu Ish Tachtav" - one must stay in an area equal to what is under himself.
Question: How much is under a person?
Answer: His body is three Amos, and we add one Amah for him to stretch his arms and legs.
R. Yehudah says, his body is three Amos. We add one Amah for him to take something from 'under' (next to) his feet [when he lies down] and put it 'above' his head.
Question: What is the difference between them?
Answer: R. Meir allows slightly more than four Amos, R. Yehudah allows [only] precisely four Amos.
Rav Mesharshiya (to his son): Ask Rav Papa if we gauge by the person's own Amah (the distance from his elbow to the end of his middle finger), or by the Amah of Hekdesh (six Tefachim. It is the same for everyone);
If he tells you that he gets four Amos of Hekdesh, ask how Og Melech ha'Bashan could manage!
If he tells you that he gets his own Amos, ask why it was not taught in the Mishnah that lists things that depend on the person himself!
Rav Papa: If we will be so meticulous [about everything, we cannot answer everything.] We will cease to learn!
(Rav Papa): He gets his own Amos. It was not taught in the Mishnah because it is not always true. One with small limbs [but average height] receives Amos of Hekdesh.
OUTER CHATZEROS THAT WERE NOT ME'AREV TOGETHER
(Mishnah): If there are two people... [if there are three, and the middle one's Amos are covered by the others'... R. Shimon says, this is like three Chatzeros...]
Question: Why must R. Shimon give an analogy?
Answer: He challenges Chachamim:
He says, this is like three Chatzeros [in a row] open to each other and open to Reshus ha'Rabim. Why do you argue with me there [and forbid all of them], and agree with me here?
Chachamim: There, there are many dwellers (it is hard to be careful not to carry things from the opposite Chatzer). Here, there are few.
(Mishnah): If the outer Chatzeros [were Me'arev with the middle Chatzer, it is permitted with them, they are permitted with it, and they are forbidden with each other].
Question: Since the outer Chatzeros were Me'arev with the middle one, they should all be like one!
Answer #1 (Rav Yehudah): The case is, the middle Chatzer put an Eruv in each of the outer ones (it is as if it lives with them, but not vice-versa).
Answer #2 (Rav Sheshes): We can even say that the outer Chatzeros put their Eruvin in the middle one, i.e. in different houses. (Therefore, they do not join.)
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. Beis Hillel are Machshir only when it is in one house, but not if it is in two.
Questions (Rav Acha brei d'Rav Avya): Both answers are difficult!
Rav Yehudah says that the middle Chatzer put an Eruv in each of the outer ones - once it put in one (e.g. the east Chatzer), they are like one. When it later puts an Eruv in the west Chatzer, it is like a Shali'ach for the east Chatzer [so now all of them should be permitted]!
According to Rav Sheshes, [since Eruv in different houses are invalid], it should be as if one of five people in a Chatzer forgot to be Me'arev. All are forbidden!
Answer (for Rav Yehudah - Rav Ashi): Since the outer Chatzeros were Me'arev with the middle one, but not with each other, this shows that they want to be Me'arev only with it, but not with each other!
Answer (for Rav Sheshes - Rav Ashi): Chachamim were lenient about Diyurin [to say that an Eruv makes it as if people live together, to allow being Me'arev together]. They did not say so to be stringent [to forbid when they put in different houses]!