Musannaf Ibn Abi Shayba 13:2307

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: Sufyan narrated to us, from Abu al-Husayn, from al-Qasim ibn ‘Abd al-Rahman: That ‘Umar disliked for the judge of the Muslims and the person in charge of their spoils of war to take a wage.