If a person arrives in the synagogue on Friday night after the congregation has recited, "Bo’i Kalla Bo’i Kalla Shabbat Malketa," he may not recite the Minha prayer in the synagogue. Since congregations accept Shabbat through the recitation of "Bo’i Kalla," an individual may not recite a weekday prayer in a synagogue that has already recited this passage, since Shabbat has already begun in the synagogue. Even though the sun has not set, and there still remains time for the recitation of Minha, it may not be recited in the synagogue, because it is a weekday prayer. In such a case, the individual must remain outside in the hallway and recite Minha there.
If, however, he arrives in the synagogue and finds that the congregation has not yet recited "Bo’i Kalla," he may pray Minha in the synagogue even though the congregation will reach the point of "Bo’i Kalla" before he completes Minha. Hacham Ovadia Yosef rules in his work Hazon Ovadia – Shabbat (vol. 1, p. 298; listen to audio recording for precise citation) that if a person begins praying Minha when this is permissible, no prohibition is entailed even if the congregation accepts Shabbat while he is still praying Minha. Thus, for example, if a person enters the synagogue as the congregation is beginning Kabbalat Shabbat, he may begin reciting Minha even though he anticipates that the synagogue will reach the point of "Bo’i Kalla" before he finishes Minha.
In such a case, one must ensure not to respond to "Barechu" with the congregation unless he has completed the Minha service. Hacham Ovadia rules that if a person answers to "Barechu" with a congregation at a Friday night Arbit service, he may no longer recite Minha, even though the sun has not set and he did not intend to accept Shabbat. Responding to "Barechu" constitutes an automatic acceptance of Shabbat regardless of a person’s intent, and one must therefore avoid responding to "Barechu" on Friday evening before reciting Minha. If one does answer to "Barechu" on Friday evening before he recited Minha, he may no longer recite Minha, and must therefore recite an extra Amida at Arbit to make up for the missed Minha.
Summary: A person who comes to the synagogue on Friday night after the congregation has recited "Bo’i Kalla" should not recite Minha inside the synagogue, and should instead recite it in the hallway. If the congregation had not yet recited "Bo’i Kalla," he may recite Minha inside the sanctuary, even though the congregation will reach "Bo’i Kalla" before he completes Minha. One who has yet to recite Minha on Friday afternoon must not respond to "Barechu" with a Minyan praying Arbit, as this constitutes the acceptance of Shabbat, such that he would be then unable to recite the Friday afternoon Minha prayer.
