Al Hijr, 99 Ayah

15:99

وَٱعۡبُدۡ رَبَّكَ حَتَّىٰ يَأۡتِيَكَ ٱلۡيَقِينُ ٩٩

Wa A`bud Rabbaka Ĥattá Ya'tiyaka Al-Yaqīnu

And worship your Lord until there comes to you the certainty (death).