Bukhari

Hadith Commentary:
In all of the aforementioned ahadith, some attribute of the Prophet (sallallahu alayhi wa sallam) has been mentioned. For this reason, these ahadith have been included under this chapter.

Hadith Commentary:
It is narrated from Anas radi Allahu anhu that the front part of the beard of the Messenger of Allah sallallahu alayhi wa sallam had, at most, twenty white hairs.
(al-Mustadrak: 2/608)
"Anfaqiyah" refers to the area between the lower lip and the chin.
Some scholars apply this term to the hairs that grow in this area. Since, linguistically, it conveys the meaning of thinness and scarcity, the word is used for a few hairs. In Urdu, this is called "daadhi bachcha" (the small beard patch). From these ahadith, it is understood that the Messenger of Allah sallallahu alayhi wa sallam had more than ten and fewer than twenty white hairs. The reconciliation between the various narrations is that the total number of white hairs on the blessed head, temples, "daadhi bachcha," and the blessed beard of the Messenger of Allah sallallahu alayhi wa sallam was, at most, twenty.
If he used oil, these white hairs would be concealed by its shine, and when he did not apply oil, they would become clearly visible. And Allah knows best.
Most likely, this was a perfection of prophethood. Nowadays, generally, by the age of forty or fifty, a person’s beard and head hair turn white.