Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
quran:43:66 –

Are they waiting except for the Hour to come upon them suddenly while they perceive not?  

Are they, that is, the Meccan disbelievers, awaiting anything, that is to say — they are ˹in fact˺ awaiting nothing — but that Hour should come upon them (an ta’tiyahum substitutes for al-sā‘ata, ‘the Hour’) suddenly, unexpectedly, while they are unaware?, of the time of its coming beforehand.
القرآن:٤٣:٦٦ –

هَلْ يَنْظُرُونَ إِلَّا السَّاعَةَ أَنْ تَأْتِيَهُمْ بَغْتَةً وَهُمْ لَا يَشْعُرُونَ  

{هل ينظرون} أي كفار مكة، أي ما ينتظرون {إلا الساعة أن تأتيهم} بدل من الساعة {بغتةً} فجأة {وهم لا يشعرون} بوقت مجيئها قبله.

See similar narrations below:

Collected by Qurʾān
quran:26:202 –

And it will come to them suddenly while they perceive ˹it˺ not.  

so that it will come upon them suddenly while they are not aware.
القرآن:٢٦:٢٠٢ –

فَيَأْتِيَهُمْ بَغْتَةً وَهُمْ لَا يَشْعُرُونَ  

{فيأتيهم بغتة وهم لا يشعرون}.
quran:47:18 –

Then do they await except that the Hour should come upon them unexpectedly? But already there have come ˹some of˺ its indications. Then what good to them, when it has come, will be their remembrance?  

Do they, then, await, they do not await, namely, the disbelievers of Mecca, anything except that the Hour should come upon them (an ta’tiyahum is an inclusive substitution for al-sā‘ata, ‘the Hour’; in other words, it cannot be other than that it will come upon them ˹…˺) suddenly? For already its portents, the signs thereof, have come, among which are the sending of the Prophet (s), the splitting of the Moon ˹Q. 54:1˺ and the Smoke ˹Q. 44:10˺. So, when it, the Hour, has come upon them, for what ˹benefit˺ will their reminder be?, their remembering; in other words, it will be of no benefit to them.
القرآن:٤٧:١٨ –

فَهَلْ يَنْظُرُونَ إِلَّا السَّاعَةَ أَنْ تَأْتِيَهُمْ بَغْتَةً ۖ فَقَدْ جَاءَ أَشْرَاطُهَا ۚ فَأَنَّىٰ لَهُمْ إِذَا جَاءَتْهُمْ ذِكْرَاهُمْ  

{فهل ينظرون} ما ينتظرون، أي كفار مكة {إلا الساعة أن تأتيهم} بدل اشتمال من الساعة، أي ليس الأمر إلا أن تأتيهم {بغتة} فجأة {فقد جاء أشرطها} علاماتها: منها النبي ﷺ وانشقاق القمر والدخان {فأنَّى لهم إذا جاءتهم} الساعة {ذكراهم} تذكرهم، أي لا ينفعهم.