Translation of the verse 97 from Surah Al-Kahf : Number of verses 110 - - page 303 - Part 16.
So they [Ya'juj and Ma'juj (Gog and Magog)] were made powerless to scale it or dig through it.
So Gog and Magog were unable to pass over it, nor were they able [to effect] in it any penetration.
(18:97) This was such a barrier that Gog and Magog could not scale over it, nor were they able to dig through it.