Musannaf Ibn Abi Shayba 18:795

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: Sufyan narrated to us, from Suhayl ibn Abi Salih, who said: I asked Sa’id ibn al-Musayyib about a free man who kills a slave intentionally. He said: I would kill him for him, humiliated and despicable.