Musnad Ahmad

Abu Kathir says that when my master, Sayyiduna Ali (may Allah be pleased with him), began fighting the people of Nahrawan, I was with him. It seemed as if the people were not happy about fighting them. Seeing this, Sayyiduna Ali (may Allah be pleased with him) said: "O people! The Prophet (peace and blessings be upon him) mentioned before us a people who would leave the religion just as an arrow leaves the bow, and they will never return to the religion until the arrow returns to the bow. The sign of these people will be that among them there will be a black man whose hand will be incomplete, and one of his hands will be like a woman's breast, and just as there is a knob on a woman's breast, so too will there be a knob on his, around which there will be a cluster of seven hairs. You should look for him among the slain; I think he will be among them." When the people searched for him, they found him under the slain by the riverbank. They pulled him out, and Sayyiduna Ali (may Allah be pleased with him) raised the slogan of "Allahu Akbar" and said: "Allah, the Lord of Might, and His Messenger have spoken the truth." At that time, Sayyiduna Ali (may Allah be pleased with him) had hung his Arabic bow; he took it in his hand and began to prick the incomplete hand with its tip, and kept saying that Allah, the Lord of Might, and His Messenger have spoken the truth. When the people saw this, they became very happy and their anger immediately vanished.