Mishkat al-Masabih 4478

Thabit reported: Anas was asked about the Prophet ﷺ dyeing his hair. He replied, “If I wanted to count the gray hairs on his head, I could do so.” He said that the Prophet ﷺ did not dye his hair. Another version adds that Abu Bakr dyed his hair with henna and katam, while Umar dyed it with pure henna.