Qur'an 18:92–101

Then followed he a route Until he came between the two mountains, beneath which he found a people who scarce understood a language. They said, "O Dhoulkarnain! verily, Gog and Magog waste this land; shall we then pay thee tribute, so thou build a rampart between us and them?" He said, "Better than your tribute is the might wherewith my Lord hath strengthened me; but help me strenuously, and I will set a barrier between you and them. Bring me blocks of iron,"--until when it filled the space between the mountain sides--"Ply," said he, "your bellows,"--until when he had made it red with heat (fire), he said,--"Bring me molten brass that I may pour upon it." And Gog and Magog were not able to scale it, neither were they able to dig through it. "This," said he, "is a mercy from my Lord: But when the promise of my Lord shall come to pass, he will turn it to dust; and the promise of my Lord is true." On that day we will let them dash like billows one over another; and there shall be a blast on the trumpet, and we will gather them together in a body. And we will set Hell on that day close before the infidels, Whose eyes were veiled from my warning, and who had no power to hear.