Tafseer Ibn Kathir of THAAHAA [129]

وَلَوْلَا كَلِمَةٌ سَبَقَتْ مِن رَّبِّكَ لَكَانَ لِزَامًا وَأَجَلٌ مُسَمًّى

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