Musnad Ahmad 33:199

Sufyan narrated to us, from ‘Amr, who heard Jabir say: "The Prophet (peace and blessings of Allah be upon him) sold a *mudabbar* slave, and Ibn al-Nahham bought him. He was a Coptic slave who died in the first year during the governorship of Ibn al-Zubayr. A man from the Ansar had made him *mudabbar*, and he had no wealth other than him."