Al-Kahf - 18:97

فَمَا اسْطَاعُوا أَن يَظْهَرُوهُ وَمَا اسْتَطَاعُوا لَهُ نَقْبًا
[18:97]
So they were not able to scale it nor could they make a hole in it.
Thus were they made powerless to scale it or to dig through it.
And (Gog and Magog) were not able to surmount, nor could they pierce (it).