Sahih Muslim Book 15, Hadith Number 4116.

Chapter : The permissibility of buying a mudabbar slave.

Jabir is reported to have said: A person amongst the Ansar who had no other property declared a slave free after his death. Allah’s Messenger (may peace be upon him) sold him, and Ibn al-Nahham bought him and he was a Coptic slave (who) died in the first year of the Caliphate of Ibn Zubair.