﴿ وَأَقْسَمُوا۟ بِٱللَّهِ جَهْدَ أَيْمَٰنِهِمْ ۙ لَا يَبْعَثُ ٱللَّهُ مَن يَمُوتُ ۚ بَلَىٰ وَعْدًا عَلَيْهِ حَقًّۭا وَلَٰكِنَّ أَكْثَرَ ٱلنَّاسِ لَا يَعْلَمُونَ ﴾

“As it is, they swear by God with their most solemn oaths, "Never will God raise from the dead anyone who has died!" Yea indeed! [This very thing has God promised] by a promise which He has willed upon Himself; but most people know it not.”

And they swear by God their most earnest oaths in other words with their utmost earnestness therein that God will not resurrect the dead. God exalted be He says Nay He will resurrect them it is a promise binding upon Him both wa‘dan and haqqan are verbal nouns used for emphasis and are in the accusative because of the verbal actions implicit in them; in other words He promised that and made it a binding truth but most people that is the people of Mecca do not know that.