Musannaf Ibn Abi Shayba 18:701

Abu Bakr narrated to us, he said: Ghundar narrated to us, from Shu'bah, from Hammad and al-Hakam, that they both said: Regarding a man who killed a slave by mistake: They both said, "It is from his wealth." And if he killed him intentionally, then it is upon the *'aqilah* (the paternal relatives).