The Book Pertaining to the Excellent Qualities of the Holy Prophet (may Peace be upon them) and His Companions (Kitab Al-Fada'il)
Muslim :: Book 30 : Hadith 5749
Anas b. Malik reported that when Allah's Messenger (may peace be upon him) had completed his dawn prayer, the servants of Medina came to him with utensils containing water, and no utensil was brought in which he did not dip his hand; and sometime they came in the cold dawn (and he did not feel reluctant in acceding to their request even in the cold weather) and dipped his hand in them.