Surah Al-Kahf, ayah 98

قَالَ هَٰذَا رَحۡمَةٞ مِّن رَّبِّيۖ فَإِذَا جَآءَ وَعۡدُ رَبِّي جَعَلَهُۥ دَكَّآءَۖ وَكَانَ وَعۡدُ رَبِّي حَقّٗا ٩٨

Qāla hādhā rahmatum mir rabbī fa idhā jā'a wa'du rabbī ja'alahū dakkā'a wakāna wa'du rabbī haqqā

[Dhul-Qarnayn] said, "This is a mercy from my Lord; but when the promise of my Lord⁷⁹⁹ comes [i.e., approaches], He will make it level, and ever is the promise of my Lord true."