(48) باب الْمَسْحِ عَلَى الْخُفَّيْنِ
Narrated Al-Mughira bin Shu`ba:
Once Allah's Messenger (ﷺ) went out to answer the call of nature and I followed him with a tumbler containing water, and when he finished, I poured water and he performed ablution and passed wet hands over his Khuffs (socks made from thick fabric or leather).
Reference: Sahih al-Bukhari 203
In-book reference: Book 4, Hadith 69
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 1, Book 4, Hadith 202