Surah Taha 20:129

وَلَوْلَا كَلِمَةٌ سَبَقَتْ مِن رَّبِّكَ لَكَانَ لِزَامًا وَأَجَلٌ مُّسَمًّى

And if not for a word that preceded from your Lord, it [i.e., punishment] would have been an obligation [due immediately], and [if not for] a specified term [decreed].

Translation: Saheeh International

Tafsir

And but for a decree that had already preceded from your Lord that their chastisement be deferred to the Hereafter it destruction would have been an inevitability their destruction would have been necessary in this world and a specified term fixed for them ajalun musamman a supplement to the pronoun concealed in kāna …

Excerpt from Tafsir al-Jalalayn, commentary on 20:129, via Quran.com. The reader has the full commentary and 9 more tafsirs.