Christ came to introduce a spiritual kingdom that was entered not by sight but only by faith. Jesus declared in John 3:3, “Verily, verily, I say unto thee, Except a man be born again, he cannot see the kingdom of God.”
This is expressly a spiritual kingdom as it relates to the spiritual realm. The blessing and rewards of the kingdom are plainly spiritual in nature and pertain exclusively to the repentant sinner. It relates to the unseen realm where the people are governed by their mediator King. A kingdom must have a king to be considered a kingdom. Christ rules this kingdom, not by force, but love. Those that subject to His authority are administered by the Word of God and the Spirit of God. Premil denies Christ His current kingship over His spiritual domain with its constant future focus upon the kinship of Christ. Whilst there is a future aspect to Christ’s kingship, there is also the current reality.
Romans 14:17-18 says, “For the kingdom of God is … righteousness and peace, and joy in the Holy Ghost. For he that in these things (1) serveth Christ (2) is acceptable to God, and (3) approved of men.”
1 Corinthians 4:20 says, “the kingdom of God is not in word, but in power (or) dunámei.”
Q. Is the redeemed Church synonymous with the kingdom of God?
A. The redeemed Church is not strictly the kingdom of God per se; it is part of the kingdom of God. The kingdom of God is a lot broader and includes the heavenly realm or territory, which evidently does not come under the more limited definition of the Church. It also includes the Godhead, which does not come under the more limited definition of the Church. It includes the righteous angelic world, which again, is clearly not the Church. The term the kingdom of God is therefore much wider than redeemed sinners – Old and New Testament, it includes the heavenly domain, it's laws, and the unseen world. The Church is restricted to redeemed human beings. Angels cannot be part of the Church, yet they are part of the kingdom.
You said:
The second coming brings a close to the day of salvation.
While that is a common doctrine in the churches, the fact is,
there are MANY passages that talk about the time AFTER the
end of the Great Commission and even passages that talk
about the time AFTER the Great Tribulation/Revelation Beasts.
Also...
There is the issue of the "Kingdoms of heaven" and the
"Kingdom of God". These are NOT the same, although
they can be used interchangeably in certain instances.
---------
The phrase "Kingdom of Heaven" is used thirty-three (33) times
in the Bible and every time the phrase represents the many unsaved "tares" and/or the few saved "wheat", associated with preaching the "Word of the Kingdom" (the Gospel) during one of the FOUR KINGDOMS on earth...
or it represents ONLY the saved "wheat" harvested into the
(5th) Eternal "Kingdom of Heaven".
The four "Kingdoms of Heaven" are physical and temporal Kingdoms...
and there's a "harvest" of Saints at the end of each, with the
"Final Harvest" including only the "Wise Virgins" living during the
(4th) Great Tribulation "Kingdom of Heaven" [Mat 25:1]
---------------------------------------------------------
The phrase "Kingdom of God" is used seventy (70) times in the
Bible and every time it represents the Holy Spirit of God and/or
the souls (but not the bodies) of the saved "wheat" who have been
regenerated by His "indwelling" Holy Spirit. To be clear, the
"Kingdom of God" is a SUBSET of the "Kingdom of Heaven" since
it only includes the saved "wheat", not the unsaved "tares".
Therefore, the Bible can use the phrases interchangeably when it focuses
only on the "wheat" within the Kingdom. When focused
only on the "wheat", the Bible can use "Kingdom of Heaven"
OR "Kingdom of God". And that is why we have several parallel passages
in the Bible that can (and do) interchange these two phrases.
-----------------------------------
All of this is BASED on the Biblical reality that JESUS specifically
NAMED separate-and-distinct "Kingdoms of Heaven" on earth.
In Matthew 22:2 Jesus specifically NAMED the Jewish
"Kingdom of Heaven" and in Matthew 21:43 Jesus specifically
NAMED the Jewish "Kingdom of God"... as it was transfered
from the Jews to the Christians.
In Matthew 13 (in 8 verses) Jesus specifically NAMED the
Christian "Kingdom of Heaven"
In Matthew 25:1 Jesus specifically NAMED the Great Tribulation
"Kingdom of Heaven"... which the church has always considered
to be PART of the Christian Kingdom but really only contained
the Last Saints who live during the Great Tribulation or the
REIGN of the Anti-Christ.
And in Matthew chapters 5 and 7 and 8 and 19 Jesus specifcally
NAMED the Eternal "Kingdom of Heaven".
-------
While the (1st) Pre-Flood "Kingdom of Heaven", which contained
all the saints from Adam to Noah, and the (2nd) Jewish Kingdom
and the (3rd) Christian Kingdom and the (4th) Great Tribulation
Kingdom all:
(1) were temporal Kingdoms and
(2) contained both saved and unsaved people
The (5th) Eternal "Kingdom of heaven" was not temporal and
contained ONLY the saved from EACH of the previous Kingdoms,
which is why we see [Mat 8:11] that Abraham, Isaac and Jacob
are part of the Eternal Kingdom when they (obviously) were not
part of the Christian Kingdom or Great Tribulation Kingdom.
-------
Just some "food for thought"...
BASED on what Jesus specifically NAMED in Scripture,
with the related verses cited above.
-------------