question #3 Sahih al-Bukhari 7175, Book 93, Hadith 39 : What significance does the Quba mosque hold in the context of early Islamic history and prayer leadership?

Salim, the freed salve of Abu Hudhaifa used to lead in prayer the early Muhajirin (emigrants) and the
companions of the Prophet (ﷺ) in the Quba mosque. Among those (who used to pray behind him) were
Abu Bakr, `Umar, Abu Salama, and Amir bin Rabi`a.