Musannaf Ibn Abi Shayba 18:939

Abu Bakr narrated to us, he said: Waki’ narrated to us, from Shu’bah, who said: I asked al-Hakam and Hammad about that. They both said: "Upon him is the blood money (diyah)." And Hammad said: "And it is reduced from him according to the extent of the wound (shajjah)."