Yajuj and Majuj is stated both in the Quran and hadith. Their appearance will be one of the signs of the end times. These events will transpire after the arrival of Dajjal, Imam Mahdi and Isa (alaihi salam). Both Quran and the hadith have clearly mentioned their existence, arrival and the aftermath of their arrival.
Gog and Magog (pronounced as “Gog u-Magog” in Hebrew and “Yajuj amd Majuj” in Arabic) are names that appear in the Old Testament, and in the Quran. Their reference in the Quran and hadith clearly indicates that they are numerous in number who will appear toward end of times.
According to the Quran, they will be set loose shortly before the arrival of the Day of Judgment as Allah Almighty has mentioned:
“Until, when Ya’jooj and Ma’jooj are let loose (from their barrier), and they swiftly swarm from every mound. And the true promise (Day of Resurrection) shall draw near (to fulfillment)…” [Surah al-Anbiyaa:96-97]
The barrier separating Yajuj and Majuj from people
Allaah Almighty tells us (interpretation of the meaning): “Then he followed (another) way, until, when he reached between two mountains, he found, before (near) them (those two mountains), a people who scarcely understood a word. They said: ‘O Dhoo’l-Qarnayn! Verily! Ya’jooj and Ma’jooj are doing great mischief in the land. Shall we then pay you a tribute in order that you might erect a barrier between us and them?’ He said: ‘That (wealth, authority and power) in which my Lord has established me is better (than your tribute). So help me with strength (of men), I will erect between you and them a barrier. Give me pieces (blocks) or iron,’ then, when he had filled up the gap between the two mountain-cliffs, he said, ‘Blow,’ till when he had made it (red as) fire, he said, ‘Bring me molten copper to pour over it.’ So they [Ya’jooj and Ma’jooj] were made powerless to scale it or dig through it. (Dhoo’l-Qarnayn) said: ‘This is a mercy from my Lord, but when the Promise of my Lord comes, He shall level it down to the ground. And the Promise of my Lord is ever true.’ And on that Day [i.e., the day Ya’jooj and Ma’jooj will come out], We shall leave them to surge like waves on one another, and the Trumpet will be blown, and We shall collect them all together.” [Surah al-Kahf 18:92-99]
Hadith is narrated by Imam Ahmed in his Musnad that the Prophet (S.A.W.S) said: “Verily, Gog and Magog dig through the dam every day, till they could see the sun rays (through it), and their leader would say: ‘Go back and you will finish it tomorrow.’ On the next day, they find it as strong as before. Till when their appointed term comes and Allah desires to send them against mankind, they dig it till they could see the sun rays (through it) and their leader says: ‘Go back and you will finish it tomorrow, if Allah wills!’ On the next day, they find it as they had left the day before and they dig through it and come against mankind. They will drink (every drop of water they pass by). The people will resort to strongholds. And, Gog and Magog will throw their arrows towards the sky. When they come back to them stained with what looks like blood, they will say: ‘We have defeated the people on earth and those in the heaven as well.’ Then, Allah the Almighty will send against them worms in their necks that will kill them all. Allah’s Messenger (S.A.W.S) said: “By Him in Whose Hand Muhammed’s soul rests! Living creatures of the earth would go fat and be thankful due to eating their flesh and (drinking their) blood.” (Also transmitted by Imam Ahmed on the authority of Hasan Ibn Musa after Sufyan after Qatadah and by At-Tirmidhi on the authority of Abu, Awanah after Qatadah.)
Destruction and death of Yajuj and Majuj by Eesa (Jesus)
After Prophet Jesus (Eesa) (P.B.U.H) will kill the Dajjal (Anti-Christ), Allah will inform him about the arrival of this disbelieving tribe that is undefeated and he will take refuge in the Mount of Toor until Allah will destroy them.
Al-Nawaas ibn Sam’aan (may Allah be pleased with him) reported that Prophet (peace and blessings of Allah be upon him), wile describing the signs of the Day of judgement said: “… and Allah will send Ya’jooj and Ma’jooj, swiftly swarming from every mound. They will pass the lake of Tiberias [in Palestine] and will drink everything that is in it. Then the last of them will pass by and will say, ‘There used to be water here once.’ The Prophet of Allah, Eesaa (Jesus), and his companions, will be besieged until a bull’s head will be more precious to one of them than a hundred dinars are to any of you today. Eesaa (Jesus) and his companions will pray to Allah, and Allah will send a kind of worm (like that found in the noses of camels and sheep) on their (Ya’jooj and Ma’jooj) necks, and they will fall down dead, all at once. Then Eesaa (Jesus) and his companions will come down out of the place where they were besieged, and they will find hardly a hand span of land that is not filled with the stench (of Ya’jooj and Ma’jooj), so Eesaa (Jesus) and his companions will pray to Allah, and He will send birds like the necks of camels to carry them away and throw them wherever Allah wills.” (Reported by Muslim, 18/68).
After the end of Gog Magog, the other signs of the arrival of day of judgment will come shortly one after another till the trumpet will be blown and the world in its present state will end (Allah SWT knows best).
https://www.youtube.com/watch?v=WxMsIBE-sb8