Musannaf Ibn Abi Shaybah

Once the mention of the Khawarij came before Hazrat Ali (may Allah be pleased with him), and he said: Among them is a man whose hand is not complete. If I did not fear that you would deny my words, I would certainly tell you that which Allah Almighty has promised, through the tongue of His Prophet (peace and blessings be upon him), to those who fight against the Khawarij. The narrator says that I asked: Did you hear this directly from the Messenger of Allah (peace and blessings be upon him)? Hazrat Ali (may Allah be pleased with him) replied: By the Lord of the Ka'bah! I heard it. He said this three times.