OPINIONS: In order to permit one to carry in a Mavoy (with a Lechi or Korah, and with Shituf Mavo'os), Rav requires that at least two houses in two Chatzeros open into the Mavoy. Shmuel says that it suffices to have one house in one Chatzer that opens into the Mavoy, with one other house that opens directly into the Mavoy without a Chatzer. Rebbi Yochanan adds that the other house that opens into the Mavoy may even be an uninhabited Churvah (a ruin). What is the Halachah?

(a) The Rishonim (TOSFOS to 12b, DH u'Batim; ROSH 6:20; see BEIS YOSEF OC 363) rule like Rav, because Rav Nachman earlier (12b) follows his opinion. Even though there is a general rule that in the laws of Eruvin, the Halachah follows the lenient opinion (and Rav's opinion is the more stringent one here), this rule applies only when Tana'im argue, but not when Amora'im argue. Furthermore, the Gemara later (74b) says that Shmuel himself accepted Rav's opinion.

(b) However, RABEINU CHANANEL rules like Shmuel and Rebbi Yochanan because of the rule that in the laws of Eruvin, the Halachah follows the lenient opinion.

(c) The RAMBAM (Hilchos Shabbos 17:8) writes that the Mavoy must have more than one house and more than one Chatzer (see also RASHI to 12b, who also says that a Mavoy needs two Chatzeros with one house in each Chatzer, or a total of two houses). The MAGID MISHNEH explains that the Rambam understands Rav to mean that it is necessary to have two Chatzeros that open into the Mavoy, and two houses that open into the Mavoy. The houses need not open into the Chatzeros.

QUESTION: Rav discusses a case in which a Nochri lives in his own Chatzer on one side of a Mavoy, and a Jew lives in his own Chatzer on the other side, and in the back of the Jew's house is a window that opens into another Jew's house (which does not open into the Chatzer in this Mavoy). In such a case, the two Jews may not make an Eruv together to permit the second Jew to carry from his house into the Mavoy via the window of the first Jew's house. Rav Yosef adds that Rav's ruling applies to a Chatzer as well that is, when the houses of the Nochri and the Jew open into a common Chatzer, and not a Mavoy, and in the back of the Jew's house is another Jew's house).

The Gemara says that had Rav Yosef not taught that Rav's ruling applies to a Chatzer as well, we might have thought that the reason why Rav does not allow an Eruv to be made to permit one to carry into the Mavoy is because the Nochri's Chatzer does not count as a Chatzer. Consequently, the Jews cannot make a Shituf, because there are not two houses in two Chatzeros opening into this Mavoy.

If this is what Rav means to say, then why does Rav choose to express this law in such a strange case, in which the house of one Jew opens through a window into the back of the house of another Jew? He should have stated his ruling in a simple case in which there are two Jewish houses opening into the Chatzer or Mavoy. The owners of those two houses cannot make a Shituf together to carry into the Mavoy because the Nochri's Chatzer does not count and thus there are not two Chatzeros in the Mavoy!

(a) TOSFOS and other Rishonim cite an answer in the name of RABEINU TAM. Rav's intention is to teach a second Halachah parenthetically -- that only when there is a Nochri on the other side of the Mavoy are the Jews prohibited to make a Shituf. When there are Jews on the other side of the Mavoy, the Jews on this side are permitted to make a Shituf, even though in this Chatzer there is only one house. Since there is a second house (behind the Chatzer) that opens into the house in the Chatzer, it is considered as though there are two houses in the Chatzer. Therefore, a Shituf may be made in such a case.

(b) Tosfos gives another answer which is the opposite of the first answer. According to the first answer, the second house that opens into the first house through a common window is considered to be in the Chatzer, so that there are two Jewish houses in the Chatzer. According to Tosfos, the second house is not considered to open into the Chatzer.

That is, Rav is not referring to a case in which there are simply two Chatzeros, one of which belongs to a Nochri, and one of which belongs to a Jew (and the Jew's house is attached to another Jew's house behind it). Rather, when Rav says "one side is Nochri, and the other side is Jewish," he means that on one side is a Nochri neighborhood with lots of Nochri residents and lots of Nochri Chatzeros (with two houses in each), and on one side is a Jewish neighborhood with lots of Chatzeros (but each one has only one Jewish house in it, and another Jewish house behind it, joined to the first through a window).

Rav is teaching that since the second house is behind the Chatzer, it is not considered to be inside the Chatzer, and thus the Mavoy is not considered to have two houses in two Chatzeros opening into it. Had the second Jew been living in the Chatzer itself, the Mavoy would have had two houses in two Chatzeros opening into it, because there are other Jewish Chatzeros here as well and all of those Chatzeros have at least two houses. Rav is teaching that the Nochri Chatzeros do not qualify (to be considered two Chatzeros with two houses), nor do the Jewish houses which join the Chatzeros through a window qualify (to be considered two houses opening into each of the many Jewish Chatzeros).

(c) Tosfos answers further and says that had the second Jew's house opened directly into the Chatzer, then the Mavoy would have contained two Jews and a Nochri. In such a case, there would have been a different reason for why a Shituf cannot be made in such a Mavoy -- because the presence of the Nochri forbids a Shituf or Eruv to be made when two or more Jews live in the same Mavoy or Chatzer with him (as the Mishnah teaches on 61b). Therefore, Rav says that even in a case where there is really only one Jew living with the Nochri (since the second Jew's house does not open into the Chatzer, but only into the first Jew's house) and the Nochri's house or Chatzer does not forbid the Jew from carrying in his Chatzer or in the Mavoy, nevertheless a Shituf may not be made. As far as the rules of Shituf are concerned, there must be two Chatzeros of Jews that open into the Mavoy, and in this case the second Chatzer belongs to a Nochri.

This explains why Rav states his ruling in a case where the second Jew's house is in back and does not open into the Chatzer. Rav is avoiding the additional problem of the Nochri's presence that would forbid the Jews from making an Eruv or Shituf.