15:99
وَٱعْبُدْ رَبَّكَ حَتَّىٰ يَأْتِيَكَ ٱلْيَقِينُ
And worship your Lord until there comes to you the certainty (death).
The Rocky Tract
وَٱعْبُدْ رَبَّكَ حَتَّىٰ يَأْتِيَكَ ٱلْيَقِينُ
And worship your Lord until there comes to you the certainty (death).
Nearby ayahs help place verse 15:99 in sequence and meaning.
وَلَقَدْ نَعْلَمُ أَنَّكَ يَضِيقُ صَدْرُكَ بِمَا يَقُولُونَ
And We already know that your breast is constrained by what they say.
فَسَبِّحْ بِحَمْدِ رَبِّكَ وَكُن مِّنَ ٱلسَّـٰجِدِينَ
So exalt [Allah] with praise of your Lord and be of those who prostrate [to Him].