Mishkat al-Masabih 5786

Thabit told that when Anas was asked about God's messenger's hair dye, he replied that [his hair] did not reach the stage of needing to be dyed, adding that if he (i.e., Anas) wanted he could count the number of grey hairs in his beard. A version says that if he wanted to count the grey hairs which were in his head he could do so. In a version he said the white hairs above his chin, on his temples and on his head were few. (Bukhari and Muslim,)