Sayyiduna Jabir (may Allah be pleased with him) said: In the head and beard of the Prophet (peace and blessings be upon him) there were only a few white hairs, and they were in the parting of his head. When he (peace and blessings be upon him) combed his beard and applied oil, they became visible, and when he left it, they were not visible.
Hadith Referenceالمعجم الكبير للطبراني / باب الجيم / 1908