The Book of Purification (Kitab Al-Taharah)
Muslim :: Book 2 : Hadith 527
Mughira b. Shu'ba reported: I was in the company of the Messenger of Allah (may peace be upon him) on a journey when he said: Mughira take hold of this jar (of water). I took hold of it and I went out with him. (I stopped but) the Messenger of Allah (may peace be upon him) proceeded on till he was out of my sight. He relieved himself and then came back and he was wearing a tight-sleeved Syrian gown. He tried to get his forearms out. but the sleeve of the gown was very narrow, so he brought his hands out from under the gown. I poured water over (his hands) and he performed ablution for prayer, then wiped over his socks and prayed.