Sahih Muslim
The Book Pertaining to the Excellent Qualities of the Holy Prophet (may Peace be upon them) and His Companions (Kitab Al-Fadail)
Book Number: 030 / Hadith Number: 5781
Muhammad b. Sirin reported: I asked Anas b. Malik whether Allah's Messenger (may peace be upon him) dyed his hair. He said: He had but little white hair.