Prayer: Performing Recommended Prayers in Congregation
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 1387
Recommended prayers cannot be performed in congregation (in some cases, however, this rule is based on obligatory precaution). [There are some exceptions,] however: ṣalāt al‑istisqāʾ, which is performed to invoke rain, can be performed in congregation. The same applies [i.e. they too can be performed in congregation] to the prayers that were obligatory and have become recommended due to some reason, such as the Eid al-Fiṭr and Eid al-Aḍḥā prayers that were obligatory when the Imam (ʿA) was present and are recommended during his occultation.