The Sages ordained that the ĥazan recite the berakha known as “Me’ein Sheva” on Friday night. This berakha is like a ĥazan’s repetition, as it is a synopsis of the seven berakhot of the Shabbat Amida. The reason for this is that synagogues were (sometimes) built in the fields, and it was dangerous to return home from them at night. The Sages were worried that if one was late or slow and finished his recitation of the Amida after the rest of the congregation, he would have to walk home alone, thus endangering himself. Therefore, they instituted that the ĥazan say this berakha in order to extend the service. This would allow those who fell behind to finish their Amida and return home with the rest of the congregation.
Even though for over a thousand years now synagogues have not been built in the fields, the ordinance stands, and in every synagogue the ĥazan recites this berakha after the Amida. However, if a minyan is convened in a private home, such as for a bridegroom or a mourner, it is not recited, since the ordinance was made only for a synagogue (SA 268:10).
Some say, however, that the talmudic Sages had an additional, esoteric rationale: on Shabbat, it is necessary to include something akin to a ĥazan’s repetition even at Ma’ariv. Consequently, the ordinance is not limited to a synagogue, but is relevant anywhere there is a minyan (Ben Ish Ĥai; Kaf Ha-ĥayim 268:50). This is the custom of those who regularly follow kabbalistic practices. But the rest of the poskim follow the first approach and maintain that Me’ein Sheva is not recited in a place that does not have a regular minyan. Only in the holy city of Jerusalem do they say Me’ein Sheva even at an impromptu minyan, because the entire city is considered a synagogue.
This berakha is the provenance of the ĥazan. Therefore, in a place where the congregation recites the stanza beginning with the words “Magen avot” aloud, the ĥazan must repeat it by himself (MB 268:22).
The Aĥaronim disagree whether the ĥazan must bow at the beginning of Me’ein Sheva. Some say that since this berakha is in lieu of the ĥazan’s repetition, it follows the same rules, and he must bow at its beginning just as he bows at the beginning of the Amida. Others maintain that it is not the same as the ĥazan’s repetition, and thus it is unnecessary for him to bow at the beginning. Everyone should follow his custom.
. If a minyan meets regularly at a specific location for several days, then according to Eliya Rabba and MB 268:24, as long as a Torah scroll is present at the minyan, Me’ein Sheva is recited. However, if there is no Torah scroll present, this berakha is not recited. In contrast, according to Igrot Moshe OĤ 4:69 (3), the key variable is not the presence of a Torah scroll but the regularity of the minyan. If it meets in the same place every Friday night, it is considered a regular minyan and Me’ein Sheva is recited. This is also implied in other Aĥaronim, including SAH 268:15, which nowhere mentions the presence of a Torah scroll as a prerequisite for determining the status of a minyan. It would seem that in any case of doubt, either because there is a disagreement about the law or because one is in doubt about the status of the minyan, one may take into account the opinion of the kabbalists and recite the berakha. Therefore, in summer camps where a Torah scroll is present, even if there is no permanent synagogue there, it is recited. In a hotel, if there is either a dedicated synagogue or a Torah scroll, it is recited. If there are neither, it is not recited. When it comes to Jerusalem, Har Tzvi (OĤ 1:152) states that anywhere there is a minyan, Me’ein Sheva is recited. Yalkut Yosef states this as well (267:20).
. The Ge’onim dispute whether one who has not prayed the Amida can fulfill his obligation by hearing the ĥazan recite Me’ein Sheva. According to R. Natronai Gaon he can, even though one who knows how to pray the Amida cannot fulfill his obligation with the ĥazan’s repetition. Since Ma’ariv was not originally obligatory, the Sages were more lenient about it. However, according to R. Moshe Gaon, only one who made a mistake and prayed a weekday Amida can fulfill his obligation by listening to Me’ein Sheva. According to R. Amram Gaon, one can never fulfill one’s Amida obligation by hearing Me’ein Sheva. At the root of their disagreement is the question of whether Me’ein Sheva can be considered the ĥazan’s repetition of the Amida. SA rules that if one heard the berakha from the ĥazan and intended to fulfill his obligation thereby, he has done so (268:13). MB states that if one made a mistake and prayed the wrong Amida, and has not yet heard Me’ein Sheva, it is better that he pray the Amida himself since there is an opinion that his obligation cannot be fulfilled through hearing Me’ein Sheva (268:28; see Yalkut Yosef 267:18).