Musannaf Ibn Abi Shayba 18:150

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: Sufyan narrated to us, 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 both of them, and in each one of them is half of the blood money. And whatever there is one of, in it is the blood money.