Musannaf Ibn Abi Shayba 13:2312

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: Mahdi ibn Maymun narrated to us, from Wasil, the freed slave of Abu ‘Uyaynah, from a man, from Ibn ‘Abbas, that a man asked him and said: "I acquired wealth from the sweeping of these latrines." He (Ibn ‘Abbas) spoke harshly to him regarding it.