And worship your Lord till you attain to the station of certainty of faith (which goes with your glory, i.e., perfect cognizance of divinity or the moment of far-nearness to your Lord)
And serve your Rabb (engage in the practices of prayer and servitude to your Rabb – the Names comprising your essential reality – while your ego self still exists) until there comes to you the certainty (until you realize the inexistence of your ego self, which is the realization of the reality of death; the experience of the Wahid’ul Qahhar. After this certainty, servitude to one’s Rabb will continue as the natural outcome of this process).
Sayyed Abbas Sadr-Ameli
And worship your Lord until the Certain comes to you.
Al-muntakhab fi tafsir al-Qur'an al-Karim
And worship Allah, your Creator, until the encounter with death which is indeed a matter of certainty