Is it permissible to pray voluntary prayers in congregation?

Question : But is it permissible to pray voluntary prayers in congregation, or do we say that that is a bid'ah (religious innovation)?

Answer : There is a distinction in this. Among the voluntary prayers, some are prescribed to be prayed in congregation, such as the prayer for rain and the eclipse prayer, if we say that the eclipse prayer is a recommended practice, and standing in night prayer in Ramadan. This is clear.
And among the voluntary prayers, some are not prescribed to be prayed in congregation, such as the rawatib (the regular voluntary prayers attached to the obligatory ones), which follow the obligatory prayers, and the night prayer in other than Ramadan. For these, congregation is not prescribed, but there is nothing wrong with praying them in congregation occasionally. The evidence for this is that the Messenger (peace and blessings be upon him) used to pray in congregation occasionally in the night prayer, as Ibn 'Abbas prayed with him, and Hudhayfah ibn al-Yaman prayed with him, and 'Abdullah ibn Mas'ud prayed with him. And occasionally he would pray in congregation until the washing of the night, as he prayed with Anas and Umm Salim.
and Taym with Anas, and as he prayed in congregation at the house of 'Atban ibn Malik (may Allah be pleased with him) when 'Atban asked the Prophet (peace and blessings be upon him) to come to him to pray in a place that 'Atban had made a prayer area, so the Prophet (peace and blessings be upon him) did so,