Sayyiduna al-Mughirah bin Shu'bah (may Allah be pleased with him) said: I was with the Messenger of Allah (peace and blessings be upon him). He (peace and blessings be upon him) went out to relieve himself, and when he had finished I brought a vessel of water. I poured water for him (peace and blessings be upon him) and he (peace and blessings be upon him) performed ablution. He (peace and blessings be upon him) was wearing a cloak with narrow sleeves, so he (peace and blessings be upon him) brought his hand out from underneath the cloak, washed his forearms and wiped over his leather socks.
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 18096