Musannaf Ibn Abi Shayba 18:1096

Abu Bakr narrated to us, he said: Muhammad ibn Bakr narrated to us, from Ibn Jurayj, he said: Ubayd Allah ibn Umar informed me that he heard some of their companions narrating that Umar ibn Abd al-Aziz began with them by [requiring] the oath, then he held them liable for the blood money (diya).