Sura 56 Al-Waqi'ah (The Inevitable), ayah 76

1. وَإِنَّهُ لَقَسَمٌ لَوْ تَعْلَمُونَ عَظِيمٌ

   And indeed, it is an oath - if you could know - (most) great.

   56:76

Translation: Saheeh International