Is supplicating in congregation impermissible?

A collective supplication (Du'a) where attendees say "Amen" to one person's supplication is permissible if it is sanctioned by the Sunnah (definition) of the Prophet, such as in prayers for rain (Istisqa) or Qunut. However, if it is performed in situations not established by the Sunnah, such as after obligatory prayers or after burying the dead, there is no harm in it if done occasionally. But, making it a continuous habit renders it an innovation (bid'ah). Imam Ahmad disliked gathering for supplication if it became a habit. The Permanent Committee for Scholarly Research and Ifta ruled that collective supplication after prayers or after meals is not permissible if it is a habit, because it was not established by the Prophet, peace and blessings be upon him.

Shaykh al-Islam Ibn Taymiyyah held that gathering for remembrance (dhikr) and supplication is good if it does not become a regular habit. Ibn Uthaymeen stated that there is no harm in collective supplication if it is not made a habit, but making it a habit renders it an innovation.