Musannaf Ibn Abi Shayba 18:1075

Abu Bakr narrated to us, he said: Isa bin Yunus narrated to us, from al-Awza’i, from Yahya bin Abi Kathir, that Ali was brought two men; one of them had killed [someone] and the other had held [the victim]. He killed the one who [had killed], and he said to the one who had held: "You held him for death, so I will hold you in prison until you die."