Can be caused by shock.
1400 years ago people thought that white hair comes from old age only. Today we know that this is false. Other factors cause change of color at any age.
Can your hair turn white as a result of shock?
Theoretically, any sudden severe shock, accident, illness or change in metabolism could make hair change colour, but it won't be visible right away.
According to Dr John O'Connor, head of the School of Physical Science and Mathematics at the University of Newcastle in Australia, "once your hair has grown out of its follicle, any emotional or physical trauma will not affect it. This hair is basically dead, like your nails. Yet severe adverse events could cause new hair that grows out a few weeks later to be white."
The Register, Can your hair turn white as a result of shock?, 2006
Shock is one of the factors that could turn hair color to white. However this was portrayed in the Quran:
[Quran 73:17] So how will you, if you persist in unbelief, save yourself from a Day which will turn the children white-haired?
Resurrection Day can cause the hair of children to turn white. Children means the cause is not old age. Today we know that the shock can turn the hair white even for children.
How could an illiterate man who lived 1400 years ago have known that shock can turn your hair white?