The ‘kingdom of God’ or ‘kingdom of heaven’ is the central theme of Jesus Christ’s preaching according to the synoptic gospels. While Matthew, who addresses himself to the Jews, speaks mostly about the ‘kingdom of heaven’, Mark and Dr Luke speak mostly about the ‘kingdom of God’ which has the same meaning as the ‘kingdom of heaven.’ Non-Jews were far more likely to understand the term ‘kingdom of God’, while it is likely that in addressing the Jews, who had strict religious rules about the use of the name of God, would have found it easier to talk about the ‘kingdom of heaven.’
John the Baptist announced in his preaching that the ‘kingdom of heaven’ was at hand. Repentance and baptism (Matt 3:11) were the steps seekers should take to prepare themselves for the coming ‘kingdom of heaven’ (Matt 3:1-2).
Jesus’ preaching focussed not only on the past and present aspects of the ‘kingdom of heaven’ but also its future aspect. In Matthew 11 verse 12 Jesus says that ‘from the days of John the Baptist until now the kingdom of heaven suffers violence, and violent men take it by force’ (NASB). The present reality is proclaimed by Jesus in Matt 12 v 28 when he says: ‘But if I cast out a demon by the Spirit of God, then the Spirit of God has come upon you.’ The miraculous activity around Jesus’ ministry was the evidence that the ‘kingdom of God’ had come to earth and was what the prophets of old had longed for (Luke 10:18-24). Jesus imparted the authority of the ‘kingdom of God’ by the word of His authority or dominion. Consequently, Christians have come to believe that the ‘king-dom of God’ is the rule and reign of Christ on earth by His command and authority. Therefore, Jesus gave His disciples a last commission before leaving the earth in Matthew 28 vs 18-20 or Mark 16 vs 17-20. Jesus Christ the Son of God had the authority to invoke the power of the rule and reign of God by the Holy Spirit in the lives of all who accept Him as the Christ of God. This rule and dominion of His Spirit in the lives of His disciples is the evidence that the ‘kingdom of God’ has come to earth.
The future evidence of the kingdom of God is the time when the demons and God-haters will be delivered up for eternal punishment in eternal darkness (Matt 8:29-34; Luke 8:17-18; Matt 4;8-10; Matt 13:38-40).
The Church is not the ‘kingdom of God,’ but the Church is the assembly of those who belong to Jesus Christ in whom His kingdom’s reign is manifest (Matt 11:25-30). The disciples of Christ have the privilege, while still on earth, to experience the manifestation of the rule and reign of Christ in their lives, which is the ‘kingdom of God.’ At a later time all disciples will live in the completeness of the ‘kingdom of God’ in heaven where Christ’s reign in their lives will be fully manifest. In the meantime experiencing the rule and reign of Christ on earth is available to all who will repent of their sinfulness (living in their own rebellious way), ask Christ to enter into their heart and change the spirit inside them by the Spirit of God ruling and reigning in their lives (John 3:3 – ‘Except one is born again he/she cannot see the kingdom of God.’ (NASB)). Muslims believe that the Kingdom of God is what God has created. Surah 7 Al Araf ayah 185 states: ‘Do they not look into the realm of the heavens and the earth and everything that Allâh has created and [think] that perhaps their appointed time has come near? So in what statement hereafter will they believe?’ The evidence that God’s reign will eventually come on earth is expressed in Surah 4 Al Nisa ayah 14: ‘But those who disobey Allâh and His Messenger and transgress His limits will be admitted to a Fire to abide therein and they shall have humiliating punishment.’ (This implies that eventually Allâh will triumph over all unbelievers).