For when they are saying, "Peace and safety," then sudden destruction will come on them, like birth pains on a pregnant woman; and they will in no way escape.

 He repeats that the coming of the day will be sudden. It will come like a thief in the night. But he also insists that that is no reason why a man should be caught unawares. It is only the man who lives in the dark and whose deeds are evil who will be caught unprepared. The Christian lives in the light and no matter when that day comes, if he is watchful and sober, it will find him ready. Waking or sleeping, the Christian is living already with Christ and is therefore always prepared. 