Musnad Ahmad 32:533

Abu Sa’id, the freed slave of Banu Hashim, narrated to us, Ishaq (Abu Ya’qub) narrated to us, he said: I heard Thabit al-Bunani, and a man asked him: "Did you ask Anas ibn Malik?" Thabit said: I asked Anas, "Did the Messenger of Allah, may Allah bless him and grant him peace, have gray hair?" He said: "Allah, the Almighty and Majestic, took His Messenger while He had not disgraced him with gray hair. There were not thirty white hairs on his head and beard on the day he died." It was said to him: "Is it a disgrace?" He said: "As for you, you consider it a disgrace, but as for us, we used to consider it an adornment."