Musannaf Ibn Abi Shayba 13:1800

Abu Bakr narrated to us, he said: Hafs bin Ghiyath narrated to us, from Hajjaj, from al-Ala’ bin Badr, from Abu Yahya al-A’raj, who said: The Prophet, peace and blessings of Allah be upon him, was asked about a slave whom his master emancipated at the time of his death, and he (the master) had no wealth other than him, and he (the master) had a debt. He said: The Prophet, peace and blessings of Allah be upon him, ordered him (the slave) to work to pay off the debt.