Qur'an 47:18

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

Await they aught save the Hour, that it should come upon them unawares? And the beginnings thereof have already come. But how, when it hath come upon them, can they take their warning?