Sayyiduna al-Mughirah bin Shu'bah (may Allah be pleased with him) said: One night I was travelling with the Messenger of Allah (peace and blessings be upon him), and he (peace and blessings be upon him) said: "Who is this?" I said: "I am al-Mughirah bin Shu'bah." He (peace and blessings be upon him) said: "Stop." So I held his she-camel for him, and he (peace and blessings be upon him) went off until he was out of sight. Then he came back and I helped him (peace and blessings be upon him) perform ablution. He (peace and blessings be upon him) uncovered his forearms, but the sleeve of the cloak was tight, so he (peace and blessings be upon him) brought his hands out from beneath it. Then he performed ablution, washing his hands, his face and his forearms, and wiped over his leather socks. I said: "Will you not remove your leather socks?" He (peace and blessings be upon him) said: "I put them on in a state of purity."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 17994