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 Safwan, from Muhammad ibn Abdillah, from al-Ridha عليه السلام, said: I asked Imam al-Ridha عليه السلام about an imam (of prayer) who is praying in a place, and those behind him are praying in a place lower than his, or he is praying in a place and those behind him are in a place higher than his. Imam عليه السلام said: “Their place should be level.” I said: “What if he is prays alone and his prostration is lower than where he stands” Imam عليه السلام said: “If he is alone, then there is no harm.”