From Sahih Bukhari (Hadith 3919):
Narrated Anas:(the servant of the Prophet) When the Prophet (ﷺ) arrived (at Medina), there was not a single companion of the Prophet (ﷺ) who had grey and black hair except Abu Bakr, and he dyed his hair with Henna' and Katam (i.e. plants used for dying hair)
Reference: Bukhari 3919