Tafsir of An-Naml 27:68

{ لقد وعدنا هذا } i.e., the aforementioned resurrection { نحن وءاباؤنا من قبل } i.e., before the promise of Muhammad, may Allah exalt him and grant him peace. The advancement of the promised object [the resurrection] before the pronoun "we" here serves to indicate that it is the very subject they intended by their speech and aimed at, as if everything else were cast aside and superfluous to it. This is evidenced by the fact that they mentioned it as originating from themselves, emphasized, affirmed, and repeated. Its delay in the verse of Surat al-Mu'minun is to preserve the original order, and there is no necessity for deviation there, as nothing was mentioned there except their following of their ancestors in disbelief and the denial of resurrection, without a specific rebuke of that against them. This sentence is an inception (istīnaf) brought forth to confirm the denial, and it is opened with an oath for added emphasis. And His saying, the Exalted: { إن هذا إلا أسطير الأولين } is a confirmation following a confirmation.