Ata bin Abi Maymunah said: I heard Sayyiduna Anas (may Allah be pleased with him) say that when the Messenger of Allah (peace and blessings be upon him) went to the toilet, I and a boy from the Ansar would follow him with a vessel of water, and he (peace and blessings be upon him) would clean himself with it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 510