The Letter Sad 38:46. Juz 23, page 456.
إِنَّآ أَخْلَصْنَـٰهُم بِخَالِصَةٍ ذِكْرَى ٱلدَّارِ٤٦
Lo! We purified them with a pure thought, remembrance of the Home (of the Hereafter).
Sad 38:46, translated by Marmaduke Pickthall