Translation of the verse 99 from Surah Al-hijr : Number of verses 99 - - page 267 - Part 14.
And worship your Lord until there comes unto you the certainty (i.e. death).
And worship your Lord until there comes to you the certainty (death).
(15:99) and serve your Lord till that last hour which is sure to come. *53
*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."
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Source : Al-hijr Verse 99: And worship your Lord until there comes to you the certainty (death).