Musnad Ahmad 33:22

'Abd al-Razzaq narrated to us, Ibn Jurayj informed us, 'Amr ibn Dinar informed us that he heard Jabir ibn 'Abd Allah saying: A man during the time of the Messenger of Allah (peace and blessings of Allah be upon him) emancipated a slave, having no wealth other than him, to take effect after his death. The Prophet (peace and blessings of Allah be upon him) said: "Who will buy him from me?" Nu'aym ibn 'Abd Allah said: "I will buy him." So he bought him. 'Amr said: Jabir said: "A Coptic slave, and he died in the first year." Abu al-Zubayr added in it: "He is called Ya'qub."