Surah Al-Infitar, ayah 18

ثُمَّ مَآ أَدۡرَىٰكَ مَا يَوۡمُ ٱلدِّينِ ١٨

Thumma mā adrāka mā yawmud-dīn

Then, what can make you know what is the Day of Recompense?