Musannaf Ibn Abi Shayba 18:194

Abu Bakr narrated to us, he said: Waki’ narrated to us, from Sufyan, from Mansur, from Ibrahim, who said: It used to be said: Whatever there are two of in a human being, the blood money (diyah) is for them, and for each one of them is half the blood money. And whatever there is one of, the blood money is for it.