Musannaf Ibn Abi Shaybah 23133 — A man who frees his slave and has no

It is narrated from Abu Yahya al-A'raj that the Prophet (peace and blessings be upon him) was asked about a slave whose master freed him at the time of his death, when he had no other wealth besides him and owed a debt (the owner, that is). The Prophet (peace and blessings be upon him) ordered that the slave should work toward his master's debt.