Musnad Ahmad 1153:1727

Waki’ narrated to us, Ibn Abi Dhi’b narrated to us, from Makhlad ibn Khuffaf ibn Ima’ ibn Rahdah al-Ghifari, from ‘Urwah, from ‘Aishah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) decreed that "the earnings of a slave are in return for his liability." Ibn Abi Dhi’b said: They had disputed regarding a slave whom a man had bought and then found a defect in him, and he had already utilized his earnings. So ‘Urwah said, from ‘Aishah: "The Messenger of Allah (peace and blessings of Allah be upon him) decreed that the earnings of a slave are in return for his liability."