Musannaf Ibn Abi Shayba 18:1061

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: Shu’bah narrated to us, he said: I asked al-Hakam and Hammad about a man who orders a man to kill a man. They both said: The killer is to be killed, and there is no retaliation (qisas) upon the one who ordered it.