Abu Dawud
Purification (Kitab Al-Taharah)
Book Number: 001 / Hadith Number: 43
Narated By Anas b. Malik : The Apostle of Allah (pbuh) entered a park. He was accompanied by a boy who had a jug of water with him. He was the youngest of us. He placed it near the lote-tree. He (the Prophet) relieved himself. He came to us after he had cleansed himself with water.