And when they had gone astray in a great error in their making the good and the bad a reason for safety from the plotting of Allah, he said, denying their safety, adding to it the saying 'they have lied' because it is the cause of the error and it is the cause of safety. He said: "Do the people of the towns feel secure?" That is: they have lied, forgetting our terrifying actions with harm and our encouraging actions with good. So they felt secure from 'our punishment' which arises from our greatness that only a loser forgets. 'By night' means: at night while they had taken comfort in their homes. And since sleep is one thing that envelops the senses and necessitates stability, he expressed it with the name indicating steadfastness, saying: 'while they are asleep' meaning: in a state of complete neglect of it.