Chapter on the Virtue of Mosques and Prayer Within Them, and the Virtue of Congregational Prayer and Its Rulings

From him, from Muhammad ibn Isa, from al-Husayn ibn Ali ibn Yaqtin, from Amr ibn Ibrahim, from Khalf ibn Hammad, from a man, from Abu Abdillah عليه السلام, peace be upon him, who said: Imam al-Sadiq عليه السلام said: “Do not pray behind the extremist (ghali), even if he claims your belief, nor behind the unknown person (majhūl, of unknown beliefs), nor behind the one who openly commits immorality (fasiq), even if he is moderate.”