Surah 73. Al-Muzzammil, Ayah 17

In ancient Arabian usage, a day full of terrifying events was described metaphorically as "a day on which the locks of children turn grey"; hence the use of this phrase in the Qur'an. Its purely metaphorical character is obvious since, according to the teachings of the Qur'an, children are considered sinless - i.e., not accountable for their doings - and will, therefore, remain untouched by the ordeals and terrors of the Day of Judgment (Razi).

If already you deny and disobey Allah in this life of probation, how can you stand up to the Day of Judgment, the Day of the terrrible Reality? That Day is described in two metaphors: (1) It will be a time of such stress that even children will become like hoary-headed men; (2) What we look upon as the eternal sky, ever the same, will be cleft asunder; cf. lxxxii. 1. In other words, the shape of things will be completely altered, both within man and in outer nature, and all true values will be restored. For the Promise of Allah, in this as in all other respects, cannot but be fulfiflled.