Musannaf Ibn Abi Shayba 1:1621

Abu Bakr narrated to us, from Ghundar and Waki’, from Shu’bah, from ‘Ata’ ibn Abi Maymunah, that he heard Anas say: The Prophet, peace and blessings of Allah be upon him, would enter the privy, and I and a boy like me would carry a water vessel and a short spear, and he would cleanse himself with water.