Isaiah 66:15 See; the Lord is coming in fire, His chariots like a whirlwind, bringing retribution in His furious anger. [ Eze 20:46-47 & Isa 33:10-12]
Isaiah 66:16 The Lord will judge with fire and His sword will test mankind. Many will be slain by them. [The Lords Day of vengeance. Isa 63:4-6 & Rev 14:17-19]
Isaiah 66:17 Those who practice magic arts, witchcraft and occult, those who eat defiled foods; they will all meet their end, for I know their deeds and thoughts.
Isaiah 66:18 I am coming to gather peoples of every tongue, they will come to see My glory. [His people, gathered into the Promised Land. Isa 11:11-12 & Zech 8:7]
Isaiah 66:19 I shall put My seal on some of those survivors. I will send them out, they will proclaim My glory among all peoples. [The 144,000 -Rev 4:1-7 & Isaiah 66:19]
Isaiah 66:20 From every nation, your brothers and sisters will be brought, on all kinds of transport, as an offering to the Lord, on His holy mountain in Jerusalem. Just as in the same way: you Israelites brought offerings to My Temple.
Isaiah 66:21 I will select some of My people to be priests and Levites.
Isaiah 66:22 As the new heavens and the new earth that I will make will endure before Me, so will your posterity and name endure.
Isaiah 66:23 Every month and every Sabbath, all mankind will come and bow down before Me. [The glory of God in the new Temple]
Isaiah 66:24 And they will all see the bodies of those who rebelled against Me, for their worm will not die, nor is the fire quenched. They will be a horror to all.
Isaiah 66:12-14 These are the words of the Lord; I shall make prosperity flow over Israel like a river. The wealth of nations will be yours. I will comfort you, as a mother comforts her child – in Zion, you will find peace. When you see this, your hearts will be glad, you will flourish. The Lord will make His power known among His servants, but His fury will be felt among His foes.
All of this passage in the last chapter of Isaiah, speaks of events that will happen before the glorious Return of Jesus. As it says in verse 14: the Lords power and fury will be known, but not His presence, at this time.
Reference; R.E.B., N.I.V. K.J.V. some verses abridged. –