Musannaf Ibn Abi Shayba 38:69

Ibn Adam narrated to us, he said: Sharik narrated to us, from Sulayman ibn al-Mughirah, from Yazid ibn Dubay'ah al-'Absi, from Ali, that he said on the Day of the Camel: "Do not pursue one who is fleeing, and do not finish off one who is wounded."