Urwah bin al-Mughirah bin Shu'bah narrates from his father (Sayyiduna al-Mughirah, may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) went to relieve himself, and I stood up; during the Battle of Tabuk I used to pour water over him (peace and blessings be upon him) from a water vessel (that is, I was assigned to serve him (peace and blessings be upon him)). He (peace and blessings be upon him) washed his face and began to wash his forearms, but the sleeves of his (peace and blessings be upon him) cloak were too tight. He brought them out from below and washed them, and wiped over his leather socks. (The same applies when resident.)
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 1298