Indeed We established him upon the earth, and We gave him to everything a way.
So he followed a way
Until, when he reached the setting of the sun, he found it [as if] setting in a spring of dark mud, and he found near it a people. Allah said, "O Dhul-Qarnayn, either you punish [them] or else adopt among them [a way of] goodness."
He said, "As for one who wrongs, we will punish him. Then he will be returned to his Lord, and He will punish him with a terrible punishment.
But as for one who believes and does righteousness, he will have a reward of Paradise, and we will speak to him from our command with ease."
Then he followed a way
Until, when he came to the rising of the sun, he found it rising on a people for whom We had not made against it any shield.
Thus. And We had encompassed [all] that he had in knowledge.
Then he followed a way
Until, when he reached [a pass] between two mountains, he found beside them a people who could hardly understand [his] speech.
They said, "O Dhul-Qarnayn, indeed Gog and Magog are [great] corrupters in the land. So may we assign for you an expenditure that you might make between us and them a barrier?"
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.
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."
So Gog and Magog were unable to pass over it, nor were they able [to effect] in it any penetration.