Tafsir of Ta-Ha 20:129

"And had it not been for a word that preceded..."

The preceding word: It is the promise to delay their recompense until the Hereafter. He says: Had it not been for this promise, the likes of our destruction of ‘Ad and Thamud would have been inevitable for these disbelievers.

"And a fixed term" (lazām):

• It is either an infinitive (maṣdar) of the verb lazima (to be inevitable), used as an adjective.
• Or it is in the form fa‘āl in the sense of muf‘il (i.e., mulzim—that which necessitates), as if it were an instrument of necessity due to its extreme persistence, just as they say lazāz khaṣm (a persistent adversary).

"And a fixed term" (wa-ajalun musammā): It must be either:

1. Conjoined to "a word" (kalimah).
2. Conjoined to the pronoun in "it would have been" (kāna).

Meaning: The immediate seizure and the fixed term would have been inevitable for them, just as they were inevitable for ‘Ad and Thamud; the fixed term is not separate from the immediate seizure.

"So be patient over what they say, and exalt [Allah] with praise of your Lord before the rising of the sun and before its setting; and during periods of the night [exalt Him] and at the ends of the day, that you may be satisfied."