Musannaf Ibn Abi Shayba 28:900

Ibn Mahdi narrated to us, from Sufyan, from Yusuf ibn Ya'qub, that a man from the polytheists killed a man from the Muslims, then entered [the Muslim territory] under a pledge of safety. Then, his [the Muslim's] brother killed him. Umar ibn Abd al-Aziz judged against him [the brother] to pay the blood money (diya), and he imposed it upon him from his own wealth, and he detained him in prison, and he sent his blood money to his heirs among the people of war.