Ali ibn Mahziyar from Faddalah from Aban from Abdul-Rahman ibn Abi Abdullah, who said: I asked Abu Abdillah عليه السلام, peace be upon him, about a man who prays while there is excrement (‘adhirah) of a human, or a cat, or a dog on his garment, does he have to repeat his prayer? Imam عليه السلام said: "If he did not know about it, then he does not have to repeat."