Musnad Ahmad 5:762

Ibn Abi ‘Adi narrated to us, from Ibn ‘Awn, from Muhammad, who said: ‘Ubaydah said: "I will not narrate to you except what I heard from him." Muhammad said: ‘Ubaydah swore to us three times, and ‘Ali swore to him: "Were it not that you would become arrogant, I would inform you of what Allah promised those who kill them, from the tongue of Muhammad, may Allah bless him and grant him peace." He said: I said: "Did you hear it from him?" He said: "Yes, by the Lord of the Ka‘bah; yes, by the Lord of the Ka‘bah; yes, by the Lord of the Ka‘bah: 'Among them is a man with a malformed hand'—or a withered hand, I think he said: 'or a defective hand.'"