فَلَنَسْأَلَنَّ الَّذِينَ أُرْسِلَ إِلَيْهِمْ وَلَنَسْأَلَنَّ الْمُرْسَلِينَ
“[On the Day of Judgment,] We will surely question those who received Messengers, and We will question the Messengers [themselves].”
The Prophet's ﷺ closing declaration ("O Allah, bear witness") here reflects this ayah's theme of messengers being questioned as witnesses over their nations.