Romans 11 neither confirms nor denies that some
people, whether Jews or Gentiles, will get saved
during the millennium.
Romans 11:26-31 refers to the salvation of all of
the unsaved elect Jews who will still be alive at
the second coming (Zechariah 12:10-14). It doesn't
say that all of their children who will be born
during the millennium won't be elect or get saved
during the millennium.
Romans 11:25 refers to a "fullness of the Gentiles"
getting saved before the second coming. It doesn't
say that more Gentiles won't get saved during the
millennium, for "fullness" doesn't have to mean
"no more after that". Even after a cup has been
filled with wine, more wine can be added to it, so
that the "cup runneth over" (Psalms 23:5b).
Isaiah 66:15-16 refers to the second coming
(2 Thessalonians 1:7-9, Revelation 19:15-21),
and Isaiah 66:18b refers to representatives from all
nations coming up to Jerusalem to see Jesus during
the millennium (Isaiah 2:1-4). Isaiah 66:19 then
refers to Jesus sending people to all the nations
during the millennium to tell about Jesus' fame and
glory in Jerusalem to all the people in those nations
who haven't heard about it yet or gone up to see it
yet. Isaiah 66:20 then refers to some of the people
who hear about it getting saved and so wanting to
come up to Jerusalem to offer themselves in service
to Jesus (cf. Romans 12:1-2). Isaiah 66:21 refers to
Jesus making them priests (cf. Revelation 5:10), and
Levites, as in temple-servants (cf. Revelation 1:1,
Luke 24:53).
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We aren't yet in the millennium (Revelation 20:4-6).
It won't start until after the second coming
(Revelation 19:11-21), and it must include those in
the church who will be beheaded by the Antichrist
during the coming tribulation for refusing to worship
him or his image or receive his mark on their hand or
forehead (Revelation 20:4, 13:7-18, 14:9-13). Those
Christians beheaded will be included in the
resurrection of the church at the second coming
(Revelation 20:4-6, 1 Corinthians 15:22-23,52,
1 Thessalonians 4:15-16), and will reign on the earth
with Jesus during the full 1000 years of the
millennium, along with the rest of the church
(Revelation 20:4-6, 5:10, 2:26-29, Matthew 19:28,
Luke 22:30). So the 1000 years can't possibly have
started yet.
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The tribulation of Revelation chapters 6-18 hasn't
started yet. It will start (possibly in 2010) with a
war which, with its aftermath of famine and epidemics,
will end up killing one-fourth of the world
(Revelation 6:4-8). The "great sword" of this war
(Revelation 6:4b) could be Israel's nuclear weapons.
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During the millennium, it will be fair for people to
choose God when there is no alternative, as in
alternative religions, for there will always be the
alternative of unbelief and rebellion (Psalms 2).
Nations will be forced to submit to Jesus during the
millennium (Psalms 66:3-7); nations will be punished
and plagued until they send delegations to come up to
worship Jesus in Jerusalem (Zechariah 14:16-19).
The devil being bound during the millennium so that
he can't deceive anyone (Revelation 20:1-3) won't
mean that people won't be tempted to sin, or won't
commit sin, during the millennium, for even though
Satan is "the tempter" (Matthew 4:3, 1 Thessalonians
3:5), people are also tempted by their own lust
(James 1:14), so that when their own lust reaches a
certain point, they commit sin (James 1:15). Sinful
actions come from within people's own wicked hearts
(Mark 7:21-23, Jeremiah 17:9). So no devil is
required for people to be tempted or to commit sin.
Some people getting saved during the millennium won't
be them getting a second chance, for as long as
someone hasn't died, their first chance is still in
effect. No one will get a second chance; if they die
in unbelief (John 3:36, 8:24) or unrepentant sin
(Hebrews 10:26-29, Luke 13:3, 1 Corinthians 9:27,
6:9-10, Galatians 5:19-21), they're lost forever;
there's no use praying for God to forgive and save
them (1 John 5:16-17).
At his second coming, Jesus will give rewards only
to those who have been saved up to that point in time
(Revelation 11:18), and only for those tasks which
they completed (Luke 12:47-48).
Revelation 22:11 is hyperbole to stress how close
the coming of Christ was even in the first century
(Revelation 22:12a,10), from the viewpoint of God
(2 Peter 3:8), who has waited so long to send Jesus
back precisely so that a lot of people would have
time to repent and get saved (2 Peter 3:9).
The "every man" of Revelation 22:12 won't be fulfilled
right at the second coming, but after the millennium
and the Gog/Magog event (Revelation 20:7-9), at the
great white throne judgment (Revelation 20:11-15),
when every unsaved person who has ever died, and
everyone who got saved during the millennium, will be
resurrected and judged according to their works, just
as those who got saved before the second coming had,
at the second coming, been resurrected and judged
according to their works (2 Corinthians 5:10, cf.
Revelation 2:23b).
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1 Corinthians 12:13 doesn't say that there won't be
baptism in the millennium. Both water baptism and
baptism in the Holy Spirit could continue in operation
during that time so that people can continue to get
saved (Mark 16:16, 1 Peter 3:21, Romans 8:9, Acts
19:2,6).
The body of Christ will be in the millennium
(Revelation 20:4-6, 5:10, 2:26-29, Matthew 19:28,
Luke 22:30).
Anyone saved during the millennium will become part
of the body of Christ, for no one can be saved apart
from faith in Christ (John 3:16,36, 14:6, Acts 4:12),
and anyone who has faith in Christ is part of the
body of Christ (Ephesians 4:4-5).
Also, anyone saved during the millennium will be saved
by the new covenant, for no one can be saved apart
from the new covenant (Matthew 26:28, 1 Corinthians
11:25, 2 Corinthians 3:6, Hebrews 9:15).
Furthermore, anyone saved during the millennium will
become part of Israel, for the new covenant by which
people are saved was made only with Israel (Jeremiah
31:31-34). This is why all Jews in the church remain
Israel (Romans 11:1), and why all Gentiles in the
church have already been grafted into Israel (Romans
11:24), made fellow citizens in Israel (Ephesians
2:12,19), made the very seed of Abraham (Galatians
3:29); so that the whole church is Israel (Revelation
21:9b,12b), just as the whole church is at the same
time the body of Christ (Ephesians 1:22-23).
Matthew 25:31-46 refers to the great white throne
judgment (Revelation 20:11-15).