Musannaf Ibn Abi Shayba 18:224

Abu Bakr narrated to us, he said: Muhammad bin Bakr narrated to us, from Ibn Jurayj, he said: Ata said regarding the hand that is severed completely: "Fifty [camels as blood money]." I said: "Is it from the shoulder joint or from the shoulder blade?" He said: "No, rather from the shoulder joint."