Japanese scientists discovered the connection between the appearence of gray hair and the hard experiences and psycological stress that a person may undergo. These scientists explained that hard experiences and, its consequent, pyscological stress lead to the damage of the hair cells, which are responsible for regulating the hair colour, and which result in gray hair. This scientific statement led me to find the Qur'anic verses which portray the same experience of gray hair and its link to hard experiences and psycological tension. In the first verses of Chapter Meriem (Mary) in Qur'an God speaks about the concerns of the Prophet Zaccharia (may God bless him) over his wife's inability to have a child that could continue the message of Prophethood. His long years of deprivation and his resulting psycological tensions are closely linked to his bones weakness and appearing gray hair. Godsays in the Holy Qur'an:
"a mention of the mercy of your Lord to His servant Zechariah,When he called to his Lord a private supplication. He said, "My Lord, indeed my bones have weakened, and my head has filled with white, and never have I been in my supplication to You, my Lord, unhappy. And indeed, I fear the successors after me, and my wife has been barren, so give me from Yourself an heir."
While the biblical tradition portrays gray head as a crown of glory that is gained in a righteous life, Qur'an, often, links gray hair to hard experiences and psycological tension. The Prophet Muhammad (peace be upon him) said:
"(Soorat) Hood and its sisters made me grey before my time."
This Hadith speaks about the revelation of the Qur'anic Chapters like Hood, Waqiaa, and other verses (that is what the Prophet means by 'its sisters': similar verses to Hood) as a reminder to the Prophet about the great responsibiliy that was thrown upon him, while in other verses it talks about the horrors of the Day of Judgement. God says in Chapter Hood talking to the Prophet Muhammad (peace be upon him):
"So stand you firm and straight (on the religion of Islamic Monotheism) as you are commanded and those (your companions) who turn in repentance (unto Allaah) with you" [Hood 11:112].
The Hadith aboved provides a clear link between the Prophet's hard experiences of Prophethood and the call to Islam, and the psycological tensions and fear it created with him, and the appearence of gray hair in him before time.
In another verses, in which God speaks about the torment of the Day of judgement, God says that even children's hair will turn gray, portraying to us the great tension and fear that people would feel in this Final day.
In a nutshell, all the Qur'anic verses which speak about gray hair in Qur'an relates it to hard experiences and psycological tension. This is a great evidence for the accuratness of the words of Qur'an, because it relies more on conveying the scientific meaning behind its statement, than delving in metaphorical explanations of physical phenomena like the gray hair.