To know the only true God, honor and obey Him, and make Him known.
What was Jesus speaking of when he talked about the kingdom of God?
There are actually different concepts in the Bible related to the phrase “kingdom of God”.
The phrase “kingdom of heaven” in the Gospel of Matthew was a Jewish expression that was used in place of “kingdom of God”. Matthew 19:16-24 demonstrates how Jesus used these phrases interchangeably. See also Matthew 11:11 and Luke 7:28.
The general concept of “kingdom of God” refers to the rule of God over all things (Psalm 103:19). Everyone and everything is under this rule during every moment (including believers and non-believers). There are no requirements to be a part of this sense of the kingdom.
There was a special Old Testament sense of the kingdom of God in His rule through certain individuals. This actually started with Adam and Eve, continued through the Patriarchs, and then was expressed through the judges, prophets, priests and kings. God was the King of the nation of Israel until they rejected Him (1 Samuel 8:7). After that point God was to rule through a king of Israel, eventually leading to a special messianic King and kingdom.
This messianic kingdom pointed to a future eternal Kingdom, related to a descendant of King David (2 Samuel 7:12-13; Isaiah 9:7). This concept is also present in the New Testament and reveals that Jesus is that King (Mark 11:9-10; Luke 1:30-33). Included in this eternal concept of kingdom is a future kingdom on Earth (Revelation 20) that will be followed by the complete realization of the eternal kingdom of God (Revelation 21; Revelation 22).
But how does this apply to us today? Jesus said that His kingdom was not of this world (John 18:36), yet Paul teaches that we are now part of the kingdom of His beloved Son (Colossians 1:13). How are we to understand this?
There is a sense in which all true believers in our present time are now part of the kingdom of God (Matthew 13). This is actually related to the present church age, the union of Jews and Gentiles in one body (Ephesians 2:11-22; Ephesians 3:1-12). All true believers today form part of the body of Christ (His church), and in a special, personal, intimate sense can participate in God’s rule over/in each of us (Ephesians 3:14-19) until the establishment of the future messianic millennial kingdom (the true and complete fulfillment when Jesus takes His place as King). [Special Note: Luke 17:21 cannot be used to support this concept because Jesus was addressing unbelieving Pharisees. The kingdom of God was certainly not “within them”, although it was “in their midst.”]
Therefore, when we invite someone today to enter the kingdom of God, we are inviting them to repent, place personal saving faith in the Lord Jesus Christ, and to actively participate in the Body of Christ, His church (Ephesians 4:11-16).