Dr. Mustafa Khattab, the Clear Quran - Surah Al-Waqi'ah, ayah 76

Translation of Surah Al-Waqi'ah, ayah 76 (56:76)

وَإِنَّهُۥ لَقَسَمٞ لَّوۡ تَعۡلَمُونَ عَظِيمٌ ٧٦
and this, if only you knew, is indeed a great oath—