What is the ruling on performing voluntary prayers in congregation?

Summary

Voluntary prayers were performed in congregation in the time of the Prophet, including the eclipse prayer, the istisqa' (rain) prayer and the Ramadan night prayer (tarawih). For other voluntary prayers such as tahiyyatul masjid, rawatib and dhuha, the fatwa cites scholars who hold that they may be prayed in congregation or individually, noting that most of the Prophet's voluntary prayers were performed alone. Imam Malik disallowed it when it becomes widely publicised and crowds are gathered, on the principle of sad al-zarai', while Ibn Habib exempted Ramadan night prayers. Shafi'i jurists state that prayers for which congregation is not recommended may still be performed in congregation.

Written in our own words from the original fatwa — check the source before acting on it.