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Eruvin 77

1) A WALL BETWEEN TWO CHATZEROS, THE TOP OF WHICH IS LESS THAN 4x4

QUESTION: Rav and Rebbi Yochanan argue concerning the status of the top of a wall between two Chatzeros, when the top of the wall is less than four by four Tefachim. Rav says that both Chatzeros have use of the top of the wall (since it is not an independent domain in itself), and therefore it is forbidden to carry even on top of the wall as in any shared domain not combined through an Eruv. Rebbi Yochanan says that each Chatzer may use the top of the wall since it is a Makom Petur.

The Gemara challenges Rebbi Yochanan's opinion from the Mishnah, which says that the residents of each Chatzer may use the top of the wall, but they might not carry things between the wall and their Chatzer.

What is the Gemara's question? The Mishnah is clearly discussing a case where the top of the wall is larger than four by four Tefachim, as the Mishnah states explicitly, while Rebbi Yochanan is talking about a wall less than four by four Tefachim! And if, for whatever reason, there is a valid question on Rebbi Yochanan from our Mishnah, then it should also be a valid question on Rav (who said that the top of the wall may not be used at all)!

ANSWERS:

(a) TOSFOS (DH Olin) answers that the Gemara knew all along that Rav's reasoning is that "both domains (the two Chatzeros) have dominion over the top of the wall," and therefore as a shared domain, it is forbidden to carry there. That applies only when it is less than four Tefachim. When it is four by four Tefachim, though, it is an independent domain unto itself and one may carry atop it, as the Mishnah states. The Gemara's question is on the opinion of Rebbi Yochanan. The Gemara initially thought that the reason Rebbi Yochanan permitted the residents of both Chatzeros to carry atop the wall is because it is not convenient for either of them to use of the top of the wall, and therefore neither Chatzer has dominion over it. If that is Rebbi Yochanan's reason, then it should apply just the same when the top of the wall is four by four Tefachim, because it is still difficult to climb up and use and it should still be considered a separate domain from each Chatzer.

The Gemara answers that Rebbi Yochanan's reasoning is not that it is difficult to use the top of the wall and therefore it is a domain unto itself, but that it is a Makom Petur. If it is wider than four Tefachim, it is no longer a Makom Petur and it is forbidden to transfer between it and the Chatzer because it is a separate domain unto itself.

(b) The CHIDUSHEI HA'RAN answers as follows. The Mishnah says that when the top of the wall is four by four Tefachim, each person may go up to the top of the wall and eat items that were already there, as long as they do not take anything down from the top of the wall. The words of the Mishnah seem to imply that the emphasis is on the Heter, that is, on what it is *permitted* to do. From that the Gemara infers that had the wall not been four by four Tefachim, it would have been completely forbidden to use the top of the wall, but now that it is four by four, there is a Heter to use it.

According to Rebbi Yochanan, who says that when it the wall is less than four by four one is permitted to eat on top of the wall and to bring food there, the Mishnah should have focused on the *Isur* and said, "One may *not* bring food up and eat it, but one may go up and eat food that was already there," placing the emphasis on what one may *not* do.

QUESTION: The Mishnah (76b) states that a wall which is at least ten Tefachim high between two Chatzeros is considered a separate Reshus from each Chatzer and the residents of the Chatzeros may not carry to or from the top of the wall. The Gemara says that if one wants to decrease the height of the wall to within ten Tefachim (making it permissible for the two Chatzeros to make an Eruv together and then to carry from each Chatzer to the top of the wall, -RITVA), one may do so by placing a mound of earth that is at least four Tefachim long (-RASHI; according to TOSFOS 77b, DH Im, it must also be four Tefachim wide) at the bottom of the wall. If the height from the top of the mound until the top of the wall is less than ten Tefachim, then the mound serves as an entranceway to the top of the wall and the entire length of the wall may be used. If the mound is less than four Tefachim long, then only the actual section of the wall against which the mound was placed may be used.

The Gemara asks that if a mound less than four Tefachim suffices, then it should permit the use of the entire length of the wall. If it does not suffice, then it should not even permit the use of the small section of wall under which it lies. Ravina answers that the Gemara is referring to when one removed a brick from the *top* of the wall. In such a case, if the removal of the brick diminished the height of the wall to less than ten Tefachim only along a section of the wall that was less than four Tefachim long, then that section of the wall is permitted to use, but not the rest of the wall.

How does this answer the Gemara's original question? What difference does it make if the decrease in height of the wall occurs as a result of raising the floor at the bottom of the wall, or lowering the height of the wall? If a mound of less than four Tefachim at the bottom of the wall does not help at all, then why should it help when the top of the wall is lowered by the amount?

ANSWERS:

(a) RASHI (DH Amar Ravina) seems to explain that when the decrease occurs at the top of the wall, even though it might not be considered an entranceway (since it is less than four Tefachim), it still serves to lower the wall at that point, and thus that section of the wall may be used. However, when a mound is placed at the bottom of the wall to decrease the wall's height, the wall itself is not actually affected because it is still ten Tefachim high (when viewed from the other side). Therefore, the section directly above the mound may not be used because it is still ten Tefachim high.

(b) The RASHBA and ROSH (7:1, near end) explain that a mound less than four Tefachim long at the *bottom* of the wall is not large enough to balance one's self on in order to use the top of the wall. Therefore the top of the wall is still considered to be ten Tefachim high. A small gap at the *top* of the wall, though, can easily be used by standing on the ground below.

Perhaps the Rashba and Rosh did not accept Rashi's explanation, because they understood that the Gemara was discussing a case of decreasing the size of the wall *from both sides* in order to make a Halachic passageway between the two Chatzeros, which would permit the two Chatzeros to make one Eruv together (as the RITVA writes).

Rashi, on the other hand, understood the Gemara not to be referring specifically to two Chatzeros that want to decrease the height of the wall between them, but even to one Chatzer which wants to decrease the height of a wall next to it (regardless of what is on the other side of the wall) in order to use the top of the wall on Shabbos. Therefore, the mound placed on one side does not serve to decrease the height of the wall, since it is still ten Tefachim high on the other side.

77b