Quran 18:98 — The Cave (Al-Kahf)

He said, "This is mercy from my Lord. When the prophecy of my Lord comes to pass, He will cause the dam to crumble. The prophecy of my Lord is truth."

[18:97] Thus, they could not climb it, nor could they bore holes in it.

[18:99] At that time, we will let them invade with one another, then the horn will be blown, and we will summon them all together.