Musannaf Ibn Abi Shayba 13:3419

Abu Bakr narrated to us, he said: Ad-Dahhak bin Makhlad narrated to us, from Ibn Jurayj, who said: I said to 'Ata': "Shall I lease my slave, that I feed him for a year, and it is for a year, and in the third [year] for such and such tribute?" He said: "There is no harm in it."