Musnad Abu Ya'la al-Mawsili 110:238

Zuhayr narrated to us, Muhammad ibn Khazim Abu Mu'awiyah narrated to us, from Hajjaj ibn Artah, from al-Hakam, from Miqsam, from Ibn Abbas, who said: The Messenger of Allah (may Allah bless him and grant him peace) emancipated on the day of Ta'if whoever came out to him from the slaves of the polytheists.