Sunan An-Nasai, Chapter: The Book of Purification

that his father said: "I was with the Prophet (saw) on a journey, and he said: 'Stay back O Mughirah! Go ahead, O people!' So I went back, and I had with me a vessel of water. The people went ahead, and there the Messenger of Allah (saw) relieved himself. When he came back I went and poured water for him. He was wearing a Roman Jubbah with narrow sleeves, and he wanted to expose his hands (to wash them) but the sleeves were too tight, so he brought his hands out from beneath the Jubbah and washed his face and hands, and wiped his head, and wiped over his Khuffs." (Sahih)