﴿ إِنَّآ أَخْلَصْنَٰهُم بِخَالِصَةٍۢ ذِكْرَى ٱلدَّارِ ﴾

“for, verily, We purified them by means of a thought most pure: the remembrance of the life to come.”

(Lo! We purified them with a pure thought) We selected them, (remembrance of the Home (of the Hereafter) for the remembrance of Allah and the remembrance of the Hereafter.