Verse 18

فَهَلْ يَنظُرُونَ إِلَّا ٱلسَّاعَةَ أَن تَأْتِيَهُم بَغْتَةً فَقَدْ جَآءَ أَشْرَاطُهَا فَأَنَّىٰ لَهُمْ إِذَا جَآءَتْهُمْ ذِكْرَىٰهُمْ

Are they then waiting for the Hour to come to them suddenly? All its necessary conditions have already been met. How could the message benefit them once it arrives?