There are various interpretations of this structure, which is generally held to denote the act of swearing an oath (so the negating particle lā is either otiose or belongs to a separate sentence). The second reading conveys this affirmed meaning with an emphatic lām [Makki]. These accord with the same skeletal structure, as the first alif may be left unpronounced. *NB: al-Bazzī from Ibn Kathīr has another narration agreeing with the majority. All readers have alif in the following ayah, which begins with the same phrase: wa-lā uqsimu.
He has revealed to you ˹O Prophet˺ the Book in truth, confirming what came before it, as He revealed the Torah and the Gospel
Explanation
There are various interpretations of this structure, which is generally held to denote the act of swearing an oath (so the negating particle lā is either otiose or belongs to a separate sentence). The second reading conveys this affirmed meaning with an emphatic lām [Makki]. These accord with the same skeletal structure, as the first alif may be left unpronounced. *NB: al-Bazzī from Ibn Kathīr has another narration agreeing with the majority. All readers have alif in the following ayah, which begins with the same phrase: wa-lā uqsimu.