Allah it is Who revealed the Book with truth, and the balance, and what shall make you know that haply the hour be nigh?

And when it was said, Surely the promise of Allah is true and as for the hour, there is no doubt about it, you said: We do not know what the hour is; we do not think (that it will come to pass) save a passing thought, and we are not at all sure.

And what would make you realize what the sure calamity is!