Prophetic authenticity

تِلْكَ ءَايَـٰتُ ٱللَّهِ نَتْلُوهَا عَلَيْكَ بِٱلْحَقِّ ۚ وَإِنَّكَ لَمِنَ ٱلْمُرْسَلِينَ

These are the verses of Allāh which We recite to you, [O Muḥammad], in truth. And indeed, you are from among the messengers.

وَيَقُولُونَ مَتَىٰ هَـٰذَا ٱلْوَعْدُ إِن كُنتُمْ صَـٰدِقِينَ

And they say, "When is this promise, if you should be truthful?"