Sayyiduna Jabir (may Allah be pleased with him) said: On the day of the Conquest of Makkah, Abu Quhafah was brought to the Prophet (peace and blessings be upon him), and his beard and head were as though they were white grass, so the Messenger of Allah (peace and blessings be upon him) said: "Dye it with something, and avoid black."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8294