Sahih Muslim Book 2, Hadith Number 526.
Chapter : Wiping over the socks.
Mughira b. Shu’ba reported: I was with the Messenger of Allah (may peace be upon him) one night. He came down (from the ride) and relieved himself. He then came and I poured water upon him from the jar that I carried with me. He performed ablution and wiped over his socks.