Musnad Ahmad 33:340

'Abd al-Razzaq narrated to us, Ma'mar narrated to us, from Layth, from Abu al-Zubayr, from Jabir, who said: Abu Quhafa was brought to the Messenger of Allah, may Allah bless him and grant him peace, on the day of the Conquest, and his head was as if it were white *thughama* (a plant with white flowers). He said: "Change this, and keep it away from black."