Musannaf Ibn Abi Shayba 18:990

Abu Bakr narrated to us, he said: Hafs narrated to us, from al-Shaybani, from al-Sha’bi, who said: A group of people from Dhurarah went out and fought one another, and they killed some of one another. Ali guaranteed the blood money for those who were killed, and he exempted the wounded [from paying blood money] in proportion to their wounds.