Musannaf Ibn Abi Shayba 13:1845

Abu Bakr narrated to us, he said: Waki’ narrated to us, from Sufyan, from Abu al-Husayn, from al-Qasim, from ‘Umar, who said: It is not appropriate for the judge of the Muslims to take a wage, nor for the one in charge of their spoils of war.