The Letter Qaf 50:29. Juz 26, page 519.
مَا يُبَدَّلُ ٱلْقَوْلُ لَدَىَّ وَمَآ أَنَا۠ بِظَلَّـٰمٍ لِّلْعَبِيدِ٢٩The sentence that cometh from Me cannot be changed, and I am in no wise a tyrant unto the slaves.
Qaf 50:29, translated by Marmaduke Pickthall