Musnad Ahmad 907:186

Abu Kamil narrated to us, Hammad narrated to us, Simak informed us, he said: I heard Jabir ibn Samurah, and it was said to him: "Was there any gray hair on the head of the Messenger of Allah, may Allah bless him and grant him peace?" He said: "There was not in his head nor in his beard except for a few hairs at the parting of his head; when he applied oil to them, the oil would conceal them."