Is the Hadith, "If you [plural] pray in your dwellings, then come to the Imam, pray with him, for it will be a supererogatory prayer for you, and that which you prayed in your dwellings will be an obligatory prayer," specific to praying in the mosque, or does it include any congregation, given that the Prophet, peace and blessings be upon him, specified the word "Imam"?

The aforementioned Hadith is authentic, and it states that whoever prays in his dwelling then comes to a congregational mosque, it is recommended for him to pray with them, and it will be a supererogatory (nafilah) prayer for him. This includes one who prayed alone, as well as one who prayed in a congregation then found another congregation; it is recommended for him to repeat the prayer with them, and it will be a supererogatory prayer for him, as the Shafi'is and Hanbalis have held.