Allah says, `do these idolaters who disbelieve in the Messengers wait'

[إِلاَّ السَّاعَةَ أَن تَأْتِيَهُمْ بَغْتَةً وَهُمْ لاَ يَشْعُرُونَ]

(only for the Hour that it shall come upon them suddenly while they perceive not) means, for it is real and will inevitably come to pass, and these negligent people are unprepared for it. When it comes, it will catch them unawares, and on that Day they will feel the utmost regret when regret will not benefit them in the slightest and will not afford them any protection.

[الاٌّخِلاَءُ يَوْمَئِذٍ بَعْضُهُمْ لِبَعْضٍ عَدُوٌّ إِلاَّ الْمُتَّقِينَ ]

(Friends on that Day will be foes one to another except those who have Taqwa.) means, every friendship that exists for a purpose other than for the sake of Allah will turn to enmity on the Day of Resurrection, except for that which is for the sake of Allah, which will last forever. This is like the statement of Ibrahim, peace be upon him, to his people:

[إِنَّمَا اتَّخَذْتُمْ مِّن دُونِ اللَّهِ أَوْثَـناً مَّوَدَّةَ بَيْنِكُمْ فِى الْحَيَوةِ الدُّنْيَا ثُمَّ يَوْمَ الْقِيَـمَةِ يَكْفُرُ بَعْضُكُمْ بِبَعْضٍ وَيَلْعَنُ بَعْضُكُمْ بَعْضاً وَمَأْوَاكُمُ النَّارُ وَمَا لَكُمْ مِّن نَّـصِرِينَ]

(You have taken (for worship) idols instead of Allah. The love between you is only in the life of this world, but on the Day of Resurrection, you shall disown each other, and curse each other, and your abode will be the Fire, and you shall have no helper.) (29:25)