﴿ قَالَ هَٰذَا رَحْمَةٌۭ مِّن رَّبِّى ۖ فَإِذَا جَآءَ وَعْدُ رَبِّى جَعَلَهُۥ دَكَّآءَ ۖ وَكَانَ وَعْدُ رَبِّى حَقًّۭا ﴾

“Said [the King]: "This is a mercy from my Sustainer! Yet when the time appointed by my Sustainer shall come, He will make this [rampart] level with the ground: and my Sustainer's promise always comes true!"”

Please check ayah 18:99 for complete tafsir.