The kingdom of God is a very large topic that would require a substantial multi-week study to even begin to properly address. In brief, the kingdom of God is based on the promise of God given to the descendants of Israel. The promises include a king that rules over Israel forever. The kingdom will begin a new golden age for Israel and usher in worldwide peace, justice and righteousness. The promise of God to David in 2 Samuel 7:16 is one of the kingdom promises, “And thine house and thy kingdom shall be established for every before thee: thy throne shall be established for ever.” The prophecies of Isaiah 11 are also kingdom prophecies, “With righteousness shall he judge the poor, and reprove with equity for the meek of the earth: and he shall smite the earth with the rod of his mouth.” “The wolf also shall dwell with the lamb, and the leopard shall lie down with the kid; and the calf and the younglionand the atling together; and a littlechild shall lead them.” “And in that daythe Lord shall set his hand again the second time to recover the remnant of His people.” “He shall set up an ensign for the nations, and shall assemble the outcasts of Israel, and gather togethe the dispersed of Judah from the four corners of the earth.”
The many kingdom promises in the Old Testament are of such a nature that an earthly, future kingdom is necessary for them to have a literal fulfillment. The Kingdom promised in the Old Testament requires a physical fulfillment. The promises of the kingdom are still waiting for fulfillment and will be fully completed when Jesus rules the world from Jerusalem.
One aspect that creates confusion is the relationship of New Testament Christians to the kingdom. Christians today are part of the kingdom. They are citizens of the kingdom that is coming. The citizenship of Christians in the kingdom does not mean the church is the kingdom, or that the kingdom promises will be spiritually accomplished in the church. The church will part of the kingdom when Jesus establishes it on the earth. The kingdom will not exist until Israel has been restored to true worship of God and all the promises made to Abraham and David are fulfilled. The kingdom will be set up exactly as has been promised through the prophets Isaiah, Jeremiah and Zechariah. We look forward to the return of Jesus and the inauguration of His earthly kingdom of righteousness and peace.