Musannaf Ibn Abi Shayba 38:34

'Abdah ibn Sulayman narrated to us, from 'Abd al-Malik ibn Sa'l, from 'Abd Khayr, who said: 'Ali ordered a herald, and he proclaimed on the Day of the Camel: "Beware, let no wounded person be finished off, and let no one who is fleeing be pursued."