Answer
The millennial kingdom is the future reign of Jesus Christ on earth as He sits on David’s throne in Jerusalem. Everyone who enters that kingdom will be redeemed by God and therefore righteous (see Isaiah 35:8–10). Among those redeemed will be two distinct groups of people: those with glorified physical bodies and those with natural, earthly bodies.
Those who occupy the millennial kingdom with glorified bodies can be divided into three subgroups: the church, whose bodies were either resurrected or changed at the rapture (1 Thessalonians 4:13–18; 1 Corinthians 15:21–23, 51–53); tribulation martyrs, who are resurrected after Christ returns to earth (Revelation 20:4–6); and the Old Testament saints, who we assume are resurrected at the same time (see Daniel 12:2). Those who occupy the kingdom with earthly bodies have survived the tribulation and can be subdivided into two groups: believing Gentiles and believing Jews.
Revelation 19:11–16 describes the second coming of Jesus Christ. This is distinct from the rapture (1 Thessalonians 4:13–18; 1 Corinthians 15:51–53), which is an earlier appearing of Christ in the air. (There is no mention in Revelation 19—20 of any kind of rapture event. This implies that saints who are on earth when Christ returns will remain on earth to enter the millennial kingdom in their natural bodies.)
Part of Jesus’ setting up the kingdom will be His judgment of the sheep and the goats (Matthew 25:31–46). The “sheep” are the righteous Gentiles, who showed their faith by their good works toward God’s people; the “goats” are the unrighteous Gentiles, who failed to aid God’s children. Christ will cast the unrighteous into the lake of fire for eternal punishment (Matthew 25:46). Because of this judgment, and because all Israel will believe at that time (Zechariah 12:10; Romans 11:25–32), no unbeliever will enter the millennial kingdom (also see Matthew 13:24–30, 36–43).
So, those who occupy the millennial kingdom, at the start, will be the righteous of all previous dispensations: believing Gentiles in earthly bodies, redeemed Israel in earthly bodies, and resurrected/raptured believers in glorified bodies. Those who occupy the millennial kingdom will be from “many nations,” but the knowledge of the Lord Jesus will be universal: “The earth will be filled with the knowledge of the Lord as the waters cover the sea” (Habakkuk 2:14). It will be standard practice for those who occupy the millennial kingdom to travel to Jerusalem and worship the Lord in person: “Many nations will come and say, ‘Come, let us go up to the mountain of the Lord, to the temple of the God of Jacob. He will teach us his ways, so that we may walk in his paths.’ The law will go out from Zion, the word of the Lord from Jerusalem” (Micah 4:2).
Those who occupy the millennial kingdom will see the nation of Israel exalted to its fullest glory. All will be restored spiritually and physically: “‘In that day,’ declares the Lord, ‘I will gather the lame; I will assemble the exiles and those I have brought to grief. I will make the lame my remnant, those driven away a strong nation’” (Micah 4:6–7).
During the millennial kingdom, the saints in earthly, natural bodies will enjoy long lives (Isaiah 65:20), and they will produce children. By the end of the thousand years, the world is fully populated, and there are many—“in number they are like the sand on the seashore”—who rebel against the Lord (Revelation 20:7–8).
Children born during the millennial kingdom will have the responsibility to exercise faith in Christ, the same as all people of past ages. Some of those born during the millennial kingdom will choose to not believe. That is why Scripture speaks of those who die under a curse (Isaiah 65:20) and why the Lord lays out consequences for nations that do not worship Him: “If any of the peoples of the earth do not go up to Jerusalem to worship the King, the Lord Almighty, they will have no rain” (Zechariah 14:17).
For a further look at who will live in the millennial kingdom, see these passages: Isaiah 2:2–4; Zechariah 14:8–21; Ezekiel 34:17–24; Daniel 7:13–14; Micah 4:1–5.
