The term “Kingdom of God” simply refers to the Dominion of King Jesus.
It is the sphere of authority, where King Jesus, who is fully God, eternally reigns. The “Kingdom of God” is the same as “the Kingdom of Heaven”.
From that time Jesus began to preach and say, “Repent, for the kingdom of heaven is at hand.” Matthew 4:17 NASB. This meant that Jesus is here now and is about to disclose the nature of his Kingdom.
The term “Kingdom of God” is synonymous with the phrase, “in Christ”.
Blessed be the God and Father of our Lord Jesus Christ, who has blessed us “in Christ” with every spiritual blessing in the heavenly places, Ephesians 1:3 ESV
The Kingdom of God has four phases.
Phase 1. God out there.
The Old Testament introduced the Kingdom of God in the first chapter of Genesis. Living in God’s Kingdom was always God’s primary plan for Adam and Eve, but they lost what they’d been given. Because of sin, Adam and Eve, as well as their family, were excommunicated from the Garden of Delight. God’s immediate presence was no longer available to them. So He drove the man out of his presence, and at the east of the garden of Eden He stationed the cherubim and the flaming sword which turned every direction to guard the way to the tree of life. Genesis 3:24 NASB But good news followed. The “God out there” was one day going to be “God with us”! Therefore the Lord himself will give you a sign. Behold, the virgin shall conceive and bear a son, and shall call his name Immanuel. Isaiah 7:14 ESV
Phase 2. The Gospels introduce “Immanuel”, (God with us).
She will bear a son, and you shall call his name Jesus, for he will save his people from their sins.” All this took place to fulfill what the Lord had spoken by the prophet: “Behold, the virgin shall conceive and bear a son, and they shall call his name Immanuel” (which means, God with us). Matthew 1:21-23 ESV
Phase 3. Kingdom rulership was available to the Church after Jesus’ resurrection. The Book of Acts introduces God, the Holy Spirit, inside us, and we inside him: but you will receive power (Kingdom authority) when the Holy Spirit has come upon you; and you shall be My witnesses both in Jerusalem, and in all Judea and Samaria, and even to the remotest part of the earth.” Acts 1:7-8 NASB
The Letters of the New Testament explain how Jesus, the “Christ”, lives inside of us and we in him. …but you are fellow citizens with the saints, and are of God’s household, having been built on the foundation of the apostles and prophets, Christ Jesus Himself being the corner stone, in whom the whole building, being fitted together, is growing into a holy temple in the Lord, in whom you also are being built together into a dwelling of God in the Spirit. Ephesians 2:19c-22.
Believers are the Temple of the Holy Spirit. To them God chose to make known how great among the Gentiles are the riches of the glory of this mystery, which is Christ in you, the hope of glory. Him we proclaim, warning everyone and teaching everyone with all wisdom, that we may present everyone mature in Christ. For this I toil, struggling with all his energy that he powerfully works within me. Colossians 1:27-29 ESV
Phase 4. Our ultimate Kingdom rulership, for which we are now in training.
“What no eye has seen, nor ear heard, nor the heart of man imagined, what God has prepared for those who love him”—1 Corinthians 2:9 ESV …and raised us up with him and seated us with him in the heavenly places in Christ Jesus, Ephesians 2:6 ESV
And there will no longer be any night; and they will not have need of the light of a lamp nor the light of the sun, because the Lord God will illumine them; and they will reign forever and ever. Revelation 22:5 NASB