Quran 18:97 from Surah Al-Kahf on Divine Marvels.
فَمَا ٱسۡطَٰعُوٓاْ أَن يَظۡهَرُوهُ وَمَا ٱسۡتَطَٰعُواْ لَهُۥ نَقۡبٗا
English translation: So not they were able to scale it and not they were able in it (to do) any penetration
Transliteration: fama is'ta'u an yazharuhu wama is'tata'u lahu naqban