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:54:30 –

And how ˹severe˺ were My punishment and warning.  

How then were My chastisement and My warnings?, My warning them of chastisement before it was sent down? In other words, it was justified. He explains it ˹their chastisement˺ by saying:
القرآن:٥٤:٣٠ –

فَكَيْفَ كَانَ عَذَابِي وَنُذُرِ  

{فكيف كان عذابي ونذر} إنذاري لهم بالعذاب قبل نزوله، أي وقع موقعه وبيَّنه بقوله.

See similar narrations below:

Collected by Qurʾān
quran:54:16 –

And how ˹severe˺ were My punishment and warning.  

How ˹dreadful˺ then were My chastisement and My warnings? (this is an interrogative meant as an affirmative; kayfa, ‘how’, is the predicate of kāna, ‘was’, and it is here being used to inquire about a ‘state’; the intention is to prompt those who are being addressed to affirm the fact that God’s chastisement of those who denied Noah was fully deserved).
القرآن:٥٤:١٦ –

فَكَيْفَ كَانَ عَذَابِي وَنُذُرِ  

{فكيف كان عذابي ونُذُر} أي إنذاري استفهام تقرير، وكيف خبر كان وهي للسؤال عن الحال والمعنى حمل المخاطبين على الإقرار بوقوع عذابه تعالى بالمكذبين لنوح موقعه.
quran:54:18 –

Aad denied; and how ˹severe˺ were My punishment and warning.  

‘Ād denied, their prophet Hūd and so they were chastised. How then were My chastisement and My warnings?, ˹how then was˺ My warning them of the chastisement before it was sent down? In other words, it was justified, and He explains this ˹chastisement˺ by saying:
القرآن:٥٤:١٨ –

كَذَّبَتْ عَادٌ فَكَيْفَ كَانَ عَذَابِي وَنُذُرِ  

{كذبت عاد} نبيهم هودا فعذبوا {فكيف كان عذابي ونذر} إنذاري لهم بالعذاب قبل نزوله أي وقع موقعه وقد بينه بقوله.