What does Isaiah 66:18 mean?

For, behold, Yahweh will come with fire, and his chariots will be like the whirlwind; to render his anger with fierceness, and his rebuke with flames of fire.

For Yahweh will execute judgment by fire and by his sword on all flesh; and those slain by Yahweh will be many.

“Those who sanctify themselves and purify themselves to go to the gardens, behind one in the middle, eating pig’s meat, abominable things, and the mouse, they shall come to an end together,” says Yahweh.

“I will set a sign among them, and I will send those who escape of them to the nations, to Tarshish, Pul, and Lud, who draw the bow, to Tubal and Javan, to far-away islands, who have not heard my fame, nor have seen my glory; and they shall declare my glory among the nations.

They shall bring all your brothers out of all the nations for an offering to Yahweh, on horses, in chariots, in litters, on mules, and on camels, to my holy mountain Jerusalem, says Yahweh, as the children of Israel bring their offering in a clean vessel into Yahweh’s house.

Of them I will also select priests and Levites,” says Yahweh.