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.”