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:78:4 –

No! They are going to know.  

No indeed! — a disavowal — they will come to know, what will befall them for their rejection of it.
القرآن:٧٨:٤ –

كَلَّا سَيَعْلَمُونَ  

{كلا} ردع {سيعلمون} ما يحل بهم على إنكارهم له.

See similar narrations below:

Collected by Qurʾān, Suyūṭī
quran:78:5 –

Then, no! They are going to know.  

Again, no indeed! They will come to know! (˹reiterated˺ for emphasis; thumma is added here to declare that the second threat of chastisement is more severe than the first). God, exalted be He, then alludes to His power to resurrect, saying:
القرآن:٧٨:٥ –

ثُمَّ كَلَّا سَيَعْلَمُونَ  

{ثم كلا سيعلمون} تأكيد وجيء فيه بثم للإيذان بأن الوعيد الثاني أشد من الأول، ثم أومأ تعالى إلى القدرة على البعث فقال: