Surah Al-Mulk (The All Authority), Verse 29

قُلْ هُوَ الرَّحْمٰنُ اٰمَنَّا بِهٖ وَعَلَیْهِ تَوَكَّلْنَا فَسَتَعْلَمُوْنَ مَنْ هُوَ فِیْ ضَلٰلٍ مُّبِیْنٍ ۟

Qul huwar rahmaanu aamannaa bihee wa 'alaihi tawakkalnaa fasata'lamoona man huwa fee dalaalim mubeen

“Say: "He is (Allah) Most Gracious: We have believed in Him, and on Him have we put our trust: So, soon will ye know which (of us) it is that is in manifest error."”

Quran 67:29 (Yusuf Ali Translation)