Understand that the KINGDOM of GOD is WITHIN US: Now when He was asked by the Pharisees when the kingdom of God would come, He answered them and said, "The kingdom of God does not come with observation; nor will they say, 'See here!' or 'See there!' For indeed, the kingdom of God is within you" (Luke 17:20-21)
The theme of the kingdom of God runs through both Testaments, focusing God’s purpose for world history. In the Old Testament God declared that He would exercise His kingship (His sovereignty, Daniel 4:34, 35) by ruling over people’s lives and circumstances through His chosen King, the Davidic Messiah (Isaiah 9:6, 7) in a golden age of blessing. This kingdom came with Jesus and is known wherever the lordship of Jesus is acknowledged. This golden age of blessing is an era of salvation from sin and fellowship with God, leading to a future state of complete joy in the “new heaven and new earth” (Rev. 21:1).
The above verses indicate that there was an aspect of kingdom promise involved in Jesus’ first coming. The kingdom of God is among earthly kingdoms today; but one day the kingdom of God will swallow up all rival kingdoms (see Rev. 11:15). In vv. 22–37, Jesus makes it clear that the kingdom has two phases—one now and one to come. In the beginning of His kingdom on earth, God first prepares a King to rule; then He gathers a people for Him to rule over; then He gives the Ruler a realm in which to reign. The kingdom now is the presence of God alongside earthly kingdoms. The power of God is shown now in the distribution and work of the Holy Spirit in His power (see 1 Cor. 4:20). One day, however, Jesus will rule over all, and He will share that rule with His people (see Rev. 2:26, 27; 5:9, 10; 20:4–6).
In contrast to the expectations of the Pharisees, the kingdom of God was not external in the political domain, but rather internal and spiritual. The phrase “within you” (v. 21) may be translated “in your midst”. The fact that the kingdom of God was in their midst meant that it was present through the person and work of Jesus who was among them. Through His death many would come to believe in Him, thereby becoming members of God’s eternal, invisible kingdom (John 3:3; Col. 1:13).
We all know that Jesus died and rose up from the dead on the third day. Before He left for His heavenly abode to be seated on the right hand of His Father, Jesus promised to send the blessed Holy Spirit to be with us in order to lead and guide us (see John 14). According to His promise, Jesus did send the blessed Holy Spirit to His church that was assembled in the upper room on the day of Pentecost (see Acts 2). From that time on, this kingdom is present in its beginnings now as the ‘Interior Kingdom’.
For many Christians, the kingdom of God is a reality to be experienced in the heart, which is the inner life of the individual believer. This reality is substantiated by the following verse: "For the kingdom of God is not eating and drinking, but righteousness and peace and joy in the Holy Spirit" (Romans 14:17). Since "flesh and blood cannot inherit the kingdom of God" (1 Cor 15:50), this kingdom is essentially a spiritual reality in a believer’s life.