Musannaf Ibn Abi Shayba 13:3418

Abu Bakr narrated to us, he said: Ad-Dahhak bin Makhlad narrated to us, from Ibn Jurayj, from ‘Ata’, regarding a man who hires a worker for a year for his food, and for a year for a specified amount of land tax (kharaj), he said: "There is no harm in it."