Inevitability and unexpectedness of Allah's justice

وَكَم مِّن قَرْيَةٍ أَهْلَكْنَـٰهَا فَجَآءَهَا بَأْسُنَا بَيَـٰتًا أَوْ هُمْ قَآئِلُونَ

And how many cities have We destroyed, and Our punishment came to them at night or while they were sleeping at noon.