Quran 56:76 from Surah Al-Waaqia on Divine Marvels.
وَإِنَّهُۥ لَقَسَمٞ لَّوۡ تَعۡلَمُونَ عَظِيمٌ
English translation: And indeed it (is) surely an oath if you know great
Transliteration: wa-innahu laqasamun law ta'lamuna azimun