(a) Hamzah bin al-Mughirah narrates from his father (may Allah be pleased with him) that he said: We were with the Messenger of Allah (peace and blessings be upon him) on a journey, and he (peace and blessings be upon him) said: "O Mughirah, stay behind, and you people, keep going." I had water with me. When the Messenger of Allah (peace and blessings be upon him) had relieved himself and returned, I poured water over him (peace and blessings be upon him). He (peace and blessings be upon him) washed his face, then began to wash his hands. He (peace and blessings be upon him) was wearing a Roman cloak whose sleeve was tight, so he (peace and blessings be upon him) brought his hands out from below, washed them, wiped his head, and also wiped over his leather socks.
(b) Urwah bin al-Mughirah narrates from his father (may Allah be pleased with him) that he said: I asked: O Messenger of Allah, do you wipe over your leather socks? He (peace and blessings be upon him) said: "I put them on while in a state of purity."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 1338