Surah At-Takathur (The Rivalry for worldly increase), Verse 5

كَلَّا لَوْ تَعْلَمُوْنَ عِلْمَ الْیَقِیْنِ ۟

Kalla law ta'lamoona 'ilmal yaqeen

“Nay, were ye to know with certainty of mind, (ye would beware!)”

Quran 102:5 (Yusuf Ali Translation)