Musannaf Ibn Abi Shayba 1:1198

Waki’ narrated to us, from ‘Abd Rabbih ibn Abi Rashid, who said: I said to Rayta, the concubine of Anas: "Did Anas use to urinate in his bathing place?" She said: "No, I used to place a vessel for him, and he would urinate in it."