DO PEOPLE IN ADJACENT CHATZEROS JOIN TOWARDS A MINYAN? [Tefilah b'Tzibur: joining]
(Mishnah): If a wide Chatzer was breached to a narrow Chatzer, the wide Chatzer is permitted, and the narrow Chatzer is forbidden, for it is like an opening of the wide one.
92b - Application #1: If the Tzibur is in the wide [enclosure], and the Shali'ach Tzibur is in the narrow one, they are Yotzei (fulfill their obligation to pray through listening to him);
If the Tzibur is in the narrow one, and the Shali'ach Tzibur is in the wide one, they are not Yoztei.
Application #2: If nine people are in the wide one, and one person is in the narrow one, they join [to form a Minyan];
If nine are in the narrow one, and one is in the wide one, they do not join.
Rosh (9:2): Also if five are in each Chatzer, they do not join. The Gemara mentioned nine in the small Chatzer for parallel structure with the Reisha, which mentioned nine in the big Chatzer.
Tosfos (92b DH Tish'ah): In Pesachim 85b, Rav Yehudah and R. Yehoshua ben Levi argue about whether a Mechitzah separates regarding Tefilah. However, here we say that it separates, and Sotah 38b connotes that the Halachah follows R. Yehoshua ben Levi! Rather, R. Yehoshua ben Levi teaches that a Mechitzah does not prevent one from answering to Birkas Kohanim or Devar shebi'Kedushah.
Rashba (Teshuvah 1:96): The law of a narrow Chatzer totally breached to a wide Chatzer applies only to separate houses, for each has its own use. Even so, if it is totally breached, it is as if the narrow Chatzer is an opening of the wide one, and people of the big Chatzer walk through the small one. If it was not totally breached, each stands by itself. We find that two groups join for a Zimun for Birkas ha'Mazon if they see each other (Berachos 50b). The same applies if they are in one building.
Shulchan Aruch (OC 55:15): If some [of the 10] are inside and some are outside, and the Shali'ach Tzibur is in the opening, he joins them.
Beis Yosef (DH v'Im): The Tur brings this from the Rosh. It seems that he learns from joining for a Zimun (Siman 195).
Gra (DH v'Im): The Yerushalmi says so about joining for a Zimun.
Prishah (7): This teaches a Chidush. Since some are here and some are there, one might have thought that he is Shali'ach Tzibur only for those inside or those outside. The Tur teaches that he is considered to be in both places. The Tur explained why below (195), for Birkas ha'Mazon, if the one who blesses stands in the threshold, he joins both, since both groups put their minds on him. Since he is Motzi them, this joins him to both groups. It is as if they sit together in one place. The same applies here with the Shali'ach Tzibur, and all the more so if nine or the majority are outside or inside, and the Shali'ach Tzibur is on the threshold, he can be Motzi them. This is only a Shali'ach Tzibur, but someone else standing on the threshold does not join them. This is not only if some are inside and some are outside. Surely, we do not consider that he is in both places. Rather, even if nine are inside and he is on the threshold, he does not join to them at all. Regarding a Beis ha'Keneses, the threshold is considered outside. If he stood outside, surely he could not join, for there is a Mechitzah and a door that one can close. It is as if it is closed. Even though even an iron wall does not separate, regarding joining, it separates. Tosfos proved this.
Eshel Avraham (12): This is better than a Zimun. There, even within one house and room, they must see each other [in order to join]. Here, within one room they need not see each other. The Mechaber (Sa'if 15) says that if some are inside and some are outside, and the Shali'ach Tzibur is in the opening, he joins them, like in Siman 195. When the one who blesses stands in the threshold, through him, it is as if they see each other. We do not require five in each room. They join even when the majority are in one place. It seems that when nine are in the Beis ha'Keneses and the Shali'ach Tzibur is in the threshold, he does not join. This is clear from Sa'if 17. If a Shali'ach Tzibur was in the big Chatzer and the Tzibur was in the small Chatzer, he is not Motzi them. We do not say that it is as if they see each other. Only when there are people in both places and he is in the middle, we say that he joins them. If the one blessing is on the threshold, if there are not people in another house, he does not join with them. We say there that if Reshus ha'Rabim interrupts, he does not join. The same applies here.
Rebuttal (R. Akiva Eiger): This is unlike the Prishah. The Prishah is correct. Eshel Avraham's proof from Sa'if 17 is wrong. He did not see the Prishah. A Shali'ach Tzibur joins them, for they put their minds on him!
Kaf ha'Chayim (80): Since there is an argument about this, one should be stringent to say that they join only in the cases that the Mechaber said.
Kaf ha'Chayim (81): The Shulchan Aruch connotes like the Pri Megadim, that even if there are a majority in one place, they join.
Mishnah Berurah (54): Since he is the Shali'ach Tzibur, everyone puts his attention on him, so he joins them. All the more so if there are nine inside and he is in the opening, he joins with them. Sa'if 17 is different. Since he is in the big Chatzer, he is separate from the Tzibur. If an individual who is not Shali'ach Tzibur is in the doorway, he does not join with them, like in Sa'if 13. This is only when they do not see each other. If some of each group sees [some of] the others, they join in every case. See below (56).
Shulchan Aruch (16): If a small Chatzer was totally breached to a big Chatzer, i.e. the entire wall between them fell, and in the big one some of the wall remained on each side, the big Chatzer is dissociated from the small Chatzer, but the small Chatzer is not dissociated from the big Chatzer. Rather, it is like a corner of it.
Kaf ha'Chayim (16): If it was not breached, this is like a Beis ha'Keneses and the Azarah (Sa'if 18).
Kaf ha'Chayim ((17): The big Chatzer is dissociated from the small Chatzer only if (the distance between the remnants of the wall) is less than 10 Amos wide (Shulchan Aruch ha'Rav 18).
Shulchan Aruch (ibid.): Therefore, if there are nine in the big Chatzer and one in the small Chatzer, they join, for the small Chatzer is drawn after the big Chatzer. It is as if it is in the big Chatzer, since the majority are in the big Chatzer.
Mishnah Berurah (55): The big Chatzer cannot be drawn after the small Chatzer, since it is like dissociated from it. Also, the Tzibur is important. It cannot be drawn after an individual. Even five cannot be drawn after five. Only an individual can be drawn after a Tzibur. Therefore, they join only if the individual is in the small Chatzer and the Tzibur is in the big Chatzer.
Shulchan Aruch (ibid.): If there are nine in the small Chatzer and one in the big Chatzer, or five in each, they do not join.
Magen Avraham (13): They do not join because it was not totally breached.
Gra (DH Im): We learn from Eruv, when there is an opening between two Chatzeros. Each is permitted by itself, since it is not totally breached.
Shulchan Aruch (17): If a Shali'ach Tzibur was in the small Chatzer and the Tzibur was in the big Chatzer, he is Motzi them, for he is drawn after them. If a Shali'ach Tzibur was in the big Chatzer and the Tzibur was in the small Chatzer, he is not Motzi them, for the majority are not drawn after the minority.
Eshel Avraham (13): The Prishah (9) says that if the Shali'ach Tzibur is on the threshold of the small [Chatzer], he joins. This is because they are not dissociated, and it looks like it is all one place. I say that the same applies to anyone on the threshold. However, if the people are in two different rooms, even a Shali'ach Tzibur does not join them.
Mishnah Berurah (56): Even if there are 10 in the small Chatzer he is not Motzi them. Even nowadays that we all know how to pray (we are not Yotzei through the Shali'ach Tzibur), he should not say Kaddish and Kedushah there, since there is not a Minyan where he stands. When there is a Minyan where he stands, surely he is Motzi even people in back of the Beis ha'Keneses who hear and intend to be Yotzei, and he intends to be Motzi all who hear him.
Shulchan Aruch (18): If some of the 10 are in the Beis ha'Keneses, and some are in the Azarah, they do not join.