And worship your Lord until there comes unto you the certainty (i.e.

﴿وَٱعۡبُدۡ رَبَّكَ حَتَّىٰ يَأۡتِيَكَ ٱلۡيَقِينُ ﴾
[الحِجر: 99]

And worship your Lord until there comes unto you the certainty (i.e. death)

﴿واعبد ربك حتى يأتيك اليقين﴾ [الحِجر: 99]

Al Bilal Muhammad Et Al
And serve your Lord until there comes to you the Hour that is certain

Ali Bakhtiari Nejad
and serve your Master until the certainty/death comes to you

Ali Quli Qarai
and worship your Lord until certainty comes to you

Ali Unal
And (continue to) worship your Lord until what is certain (death) comes to you

Hamid S Aziz
And serve your Lord until there comes unto you the Hour that is certain (death)

John Medows Rodwell
And serve thy Lord till the certainty o'ertake thee

Literal
And worship your Lord, until the assurance/certainty (death) comes to you

Mir Anees Original
And serve your Fosterer till that which is certain comes to you

Mir Aneesuddin
And serve your Lord till that which is certain comes to you