18:97
فَمَا ٱسْطَـٰعُوٓا۟ أَن يَظْهَرُوهُ وَمَا ٱسْتَطَـٰعُوا۟ لَهُۥ نَقْبًۭا
So Gog and Magog were unable to pass over it, nor were they able [to effect] in it any penetration.
The Cave
فَمَا ٱسْطَـٰعُوٓا۟ أَن يَظْهَرُوهُ وَمَا ٱسْتَطَـٰعُوا۟ لَهُۥ نَقْبًۭا
So Gog and Magog were unable to pass over it, nor were they able [to effect] in it any penetration.
Nearby ayahs help place verse 18:97 in sequence and meaning.
قَالَ مَا مَكَّنِّى فِيهِ رَبِّى خَيْرٌۭ فَأَعِينُونِى بِقُوَّةٍ أَجْعَلْ بَيْنَكُمْ وَبَيْنَهُمْ رَدْمًا
He said, "That in which my Lord has established me is better [than what you offer], but assist me with strength; I will make between you and them a dam.
ءَاتُونِى زُبَرَ ٱلْحَدِيدِ ۖ حَتَّىٰٓ إِذَا سَاوَىٰ بَيْنَ ٱلصَّدَفَيْنِ قَالَ ٱنفُخُوا۟ ۖ حَتَّىٰٓ إِذَا جَعَلَهُۥ نَارًۭا قَالَ ءَاتُونِىٓ أُفْرِغْ عَلَيْهِ قِطْرًۭا
Bring me sheets of iron" - until, when he had leveled [them] between the two mountain walls, he said, "Blow [with bellows]," until when he had made it [like] fire, he said, "Bring me, that I may pour over it molten copper."
قَالَ هَـٰذَا رَحْمَةٌۭ مِّن رَّبِّى ۖ فَإِذَا جَآءَ وَعْدُ رَبِّى جَعَلَهُۥ دَكَّآءَ ۖ وَكَانَ وَعْدُ رَبِّى حَقًّۭا
[Dhul-Qarnayn] said, "This is a mercy from my Lord; but when the promise of my Lord comes, He will make it level, and ever is the promise of my Lord true."
۞ وَتَرَكْنَا بَعْضَهُمْ يَوْمَئِذٍۢ يَمُوجُ فِى بَعْضٍۢ ۖ وَنُفِخَ فِى ٱلصُّورِ فَجَمَعْنَـٰهُمْ جَمْعًۭا
And We will leave them that day surging over each other, and [then] the Horn will be blown, and We will assemble them in [one] assembly.