And worship your Lord until there comes to you the certainty (death). (15:99)

Almuntakhab Fi Tafsir Alquran Alkarim

And worship Allah, your Creator, until the encounter with death which is indeed a matter of certainty

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(15:99) and serve your Lord till that last hour which is sure to come. *53

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

*53) That is Salat and worship of your Lord are the only means which can generate in you that power of sustenance which is required to stand resolutley against the troubles and afflictions you will inevitably encounter in the propagation of the Message of the Truth and reform of humanity. This will comfort you, fill you with courage and enable you to perform that Divine Mission on which you have been sent in the face of abuse, derision and obstacles."

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

اور اُس آخری گھڑی تک اپنے رب کی بندگی کرتے رہو جس کا آنا یقینی ہے