Forgot to add the Qur'an ayat and hadith :
So Ya'juj and Ma'juj were unable to pass over it, nor were they able [to effect] in it any penetration. [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." (Al-Kahf 97-98)
An-Nawwas bin Sam`an (May Allah be pleased with him) narrated :
Allah will reveal to `Isa these words: `I have brought forth from amongst my slaves such people against whom none will be able to fight, so take these people safely to the mountain.' And then Allah will send Ya'juj and Ma'juj (Gog and Magog people) and they will sworn down from every slope. The first of them will pass the Lake Tabariyah (near the Dead Sea in Palestine) and drink all its water. And when the last of them will pass, he will say: `There was once water there.' Prophet `Isa (ﷺ) and his companions will then be so much hard-pressed that the head of an ox will be dearer to them than one hundred dinar, and `Isa along with his companions, will make supplication to Allah, Who will send insects which will attack their (Ya'juj and Ma'juj people) neck until they all will perish like a single person. Prophet, `¦sa and his companions will then come down and they will not find in the earth as much space as a single span which would not be filled with their corpses and their stench. Prophet `Isa and his companions will then again beseech Allah, Who will send birds whose necks will be like those of Bactrian camels, and they will carry them and throw them where Allah will desire. (Sahih Muslim)