Surah Al-Kahf, Verse 98
قَالَ هَٰذَا رَحْمَةٌۭ مِّن رَّبِّى ۖ فَإِذَا جَآءَ وَعْدُ رَبِّى جَعَلَهُۥ دَكَّآءَ ۖ وَكَانَ وَعْدُ رَبِّى حَقًّۭا
Translation — Sahih International
[Dhul-Qarnayn] said, "This is a mercy from my Lord; but when the promise of my Lord comes, He will make it level, and ever is the promise of my Lord true."
Source
Kur'an-ı Kerim, Kehf Suresi 18:98
https://kuran.diyanet.gov.tr/mushaf/kuran-meal-2/18-suresi-98-ayet