Musnad Ahmad 5:173

Waki’ narrated to us, Jarir ibn Hazim and Abu ‘Amr ibn al-‘Ala’ narrated to us, from Ibn Sirin, who heard it from ‘Ubaydah, from ‘Ali, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "A people will emerge among whom there is a man with a deformed hand—or a withered hand, or a truncated hand. And were it not that you would become arrogant, I would have informed you of what Allah has promised those who kill them, upon the tongue of His Prophet (peace and blessings of Allah be upon him)." ‘Ubaydah said: I said to ‘Ali: Did you hear it from the Messenger of Allah (peace and blessings of Allah be upon 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!