Musannaf Ibn Abi Shayba 18:731

Abu Bakr narrated to us, he said: Ibn ‘Uyaynah narrated to us, from Sadaqah ibn Yasar, from Sa’id ibn al-Musayyib, who said: ‘Uthman decreed regarding the blood money (diyah) of a Jew and a Christian to be four thousand dirhams.