Sahih Bukhari
Ablutions (Wudu)
Volume: 001 / Book Number: 004 / Hadith Number: 202
Narrated Al-Mughlra bin Shu'ba:
Once Allah's Apostle 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.