The Hair:

 Dear brothers, it is well known that in the top part of our heads, there are 100 – 250 thousand hairs. The average life of a hair is approximately 3 years; and we need 200 days in order to have all of our hair renewed.
 In fact, in our human body there are as many hair factories as there are hairs. In other words, each and every hair in our body has its own factory, in which the hair is produced, lives and grows and then dies.
 Each hair has a vein, an artery for nutrition, and a muscle for movement (which works when one feels cold). Each hair also has a nerve (which helps it stand on end), a fat gland, and a dye gland.

Causes of hair whiteness

 No researcher so far knows why our hair grows white. But in some recent studies, it is claimed that whiteness of hair has to do with our nervous system and condition and that the white cells of the blood sneak into the hair and devour its black dye. The definitive opinion recently advocated by doctors, however, is that whiteness of hair is considered as a skin disease and it has to do with the person’s nervous and emotional condition.
 Remarkably, this definitive opinion, which is advocated by a great many medical doctors, is mentioned in Allah’s Miraculous Book, the Noble Quran, which was revealed more than 1400 years ago. Allah, All Mighty, says,

“Then how can you avoid the punishment, if you disbelieve, on a Day that will make the children grey-headed (i.e. the Day of Resurrection)?.”

[Al-Muzzamil, 17]

 This Ayah shows clearly that whiteness of hair is caused by fear. To this effect, Ibn ‘Abbas narrated that the venerable Companion, Abu Bakr As-Siddeeq, may Allah be pleased with him, once asked Allah’s Messenger, (PBUH), “O Messenger of Allah! Your hair has grown white.” Allah’s Messenger, (PBUH), answered,

“It is Houd, Al-Waqi’ah, Al-Moursalat, ‘Amma Yatasa’aloun, and Itha Shamsou Kouwirat that made me white-haired.”

[At Tirmizi]

 Yes, indeed! Surat Houd turned the Prophet’s hair white, perhaps because in one of its Ayat the Lord, All Mighty, bade him:

“So stand (ask Allah to make) you (Muhammad ) firm and straight (on the religion of Islamic Monotheism) as you are commanded and those (your companions) who turn in repentance (unto Allah) with you, and transgress not (Allah's legal limits). Verily, He is All-Seer of what you do.”

[Hud,112]

 Also, as one grows old, this means that one has suffered a lot of nervous stress, and, therefore, one’s hair turns white (The number of white hairs differs from one person to another though). In this context, Allah, All Mighty, says:

“Allah is He Who created you in (a state of) weakness, then gave you strength after weakness, then after strength gave (you) weakness and grey hair. He creates what He wills. And it is He Who is the All-Knowing, the All-Powerful (i.e. Able to do all things).”

[Ar-Rum, 54]

 In fact, whiteness of hair usually accompanies old age; and the well-known Imam, Al-Qourtubi, considered that as a kind of warning, as in Allah’s Words,

“And the Warning has come to you”.

 He, may Allah have mercy on him, said, “The Warning mentioned in this Quranic Ayah is whiteness of hair, whereby Allah, Most Gracious, calls His slave’s attention to the fact that the encounter with The Lord has drawn near, so what has he prepared for it.” To the same effect, a Divine Hadith goes:

“O My slave! Your vision has grown weak, your hair has grown white, and your back has grown bent down! So, be shy with Me, as I am shy with you!”

The hair of the head and eyebrows: 

Dear brothers, here is a delicate question that confirms Allah’s Infinite Divine Wisdom: Why does the head’s hair grow, while that of the eyebrows and eyelids does not grow?! Why does hair grow inside the nose and not inside the mouth?! Why does hair grow on the outer part of the hand and not on the palm?!

It is really amazing how Allah is disobeyed,
Or how those deniers deny Him!
In everything He has a Sign,
Bespeaking His Oneness!
* * *

Your hair is a wonder Allah gave you, so reflect on it and make it your path to reach Allah Almighty, only then you will realize that man is created by Great Creator and Wise Maker Who perfected His creation and everything He created:

"Were they created by nothing, or were they themselves the creators?"

[At-Tur, 35]