KINGDOM OF GOD / KINGDOM OF HEAVEN
The Synoptic gospels use the kingdom of God and the Kingdom of Heaven. Both mean the same. Matthew preferred the Kingdom of heaven because he wanted to avoid the word “God” that his Jewish readers would not use. In a broader sense, both refer primarily to the rule of the Almighty over all the entire universe with no territory because everything belongs to God with no border. “The LORD has set his throne in heaven; his dominion extends over all” (Ps 103:19).
In a specific sense, Israel was the kingdom of God because God’s kingdom is a spiritual rule over the lives and hearts of those who remain faithful to God. Jesus reconstituted it, forming the church with Jesus as its head. This kingdom is spiritual, and that is why Jesus said to Pilate: “My kingdom does not belong to this world” (Jn 18:36).
The church is only a foretaste of God’s kingdom that will happen later in its fullness when the time of redemption is over and when the time of judgement will arrive with the second coming of Christ. God governs this kingdom. It is eternal, peaceful, free from any struggle, and is open only for the faithful children of God. “In the lifetime of those kings the God of heaven will set up a kingdom that shall never be destroyed or delivered up to another people; rather, it shall break in pieces all these kingdoms and put an end to them, and it shall stand forever” (Dan 2:44).
The Kingdom of God has distinct stages: God initially established it in the world at large, then among the chosen people of Israel, Jesus renewed it later by establishing the church, and it will come to its perfection with the second coming of Christ.
Christians are already in the Kingdom of God that Jesus established. We gained citizenship in this kingdom through baptism and our faith. After our life in this world, we are looking forward to enter the perfect experience of the kingdom in heaven. That gives us hope during our struggles in this world.