Musannaf Ibn Abi Shayba 28:904

Jarir narrated to us, from Mughira, from Ibrahim, who said: "Regarding [the verse]: 'But if he is from a people who are enemies to you while he is a believer,' the man is killed while his people are polytheists, and there is no treaty between them and the Messenger of Allah (peace and blessings of Allah be upon him), so the expiation is the freeing of a believing slave. If a Muslim is killed by a people who are polytheists, and there is a treaty between them and the Messenger of Allah (peace and blessings of Allah be upon him), then upon him [the killer] is [the freeing of] a believing slave, and his blood money (diya) is to be paid to his people who have a treaty with the Messenger of Allah (peace and blessings of Allah be upon him). His inheritance shall be for the Muslims, and his blood money (aqilah) shall be upon them—meaning his polytheist people who have a treaty with the Messenger of Allah (peace and blessings of Allah be upon him). So the Muslims inherit his inheritance, and his blood money is upon his people, because they are responsible for his blood money (ya'qiluna 'anhu)."