Answer
The millennium, also known as the millennial kingdom, is the 1,000-year reign of Jesus after the tribulation and before the Great White Throne Judgment of the wicked. During the millennium, Jesus will reign as king over Israel and all the nations of the world (Isaiah 2:4; Isaiah 42:1). The world will live in peace (Isaiah 11:6-9; 32:18), Satan will be bound (Revelation 20:1-3), and initially, everyone will worship God (Isaiah 2:2-3). The purpose of the 1,000-year reign is to fulfill various promises God made to the world. Some of these promises, known as covenants, were specifically given to Israel. Others were made to Jesus, the nations of the world, and creation. Jesus’ 1,000-year reign will be a time of promises fulfilled.
The Palestinian Covenant, also known as the Land Covenant (Deuteronomy 30:1-10)
God has already fulfilled the personal aspects of the Abrahamic Covenant; Abraham did go to the Promised Land, he did have many descendants, and he is the forefather of many nations. Several hundred years after Abraham, Joshua led the Israelites to claim ownership of the Promised Land. However, Israel has never possessed the specific boundaries that God promised in Genesis 15:18–20 and Numbers 34:1-12. Not even Solomon ruled over this particular area (1 Kings 4:21-24). Although he reigned from the River of Egypt to the Euphrates, he did not control the area from Mount Hor to Hazarenan (Numbers 34:7-9)—extending into present-day Lebanon and Syria. Furthermore, the covenant God established with Abraham was that he and his descendants would possess the land forever (Genesis 13:15; Genesis 17:8; Ezekiel 16:60). The current state of Israel may be a step in this direction, but they have not yet acquired the boundaries God specified.
The Davidic Covenant (2 Samuel 7)
God’s covenant with David ensured that his lineage would never cease and that David’s descendant would rule over Israel eternally «And thine house and thy kingdom shall be established for ever before thee: thy throne shall be established for ever. », (2 Samuel 7:16). Biblical scholars concur that Jesus fulfills this covenant—one reason His genealogy is provided for both His legal father (Matthew 1:1-17) and His mother (Luke 3:23-38). The Jewish people recognized this when they laid palm branches and their cloaks as Jesus entered Jerusalem (Matthew 21:1-17). They anticipated Him to be a military or political leader who would free them from the Romans and restore Israel to its former glory. However, they did not grasp that Jesus’ mission at that time was for the New Covenant, not the Davidic Covenant. The thousand-year reign will mark the commencement of Jesus’ rule over Israel and the earth «And I saw thrones, and they sat upon them, and judgment was given unto them: and II saw the souls of those who were beheaded for the testimony of Jesus and for the word of God. They had not worshiped the beast or its image and had not received its mark on their foreheads or hands. They came to life and reigned with Christ for a thousand years. », (Revelation 20:4,6) «Blessed and holy is the one who shares in the first resurrection! Over such the second death has no power, but they will be priests of God and of Christ, and they will reign with him for a thousand years. », (Revelation 20:4,6).
The New Covenant (Jeremiah 31:31-34)
The work of the New Covenant—Jesus’ death and resurrection to reconcile hearts to God—has been accomplished. However, we have not yet witnessed its complete fulfillment. Jeremiah 31:33 states, “But this is the covenant that I will make with the house of Israel after those days, declares the LORD: I will put my law within them, and I will write it on their hearts. And I will be their God, and they shall be my people.” Ezekiel 36:28 provides more details: “You shall dwell in the land that I gave to your fathers, and you shall be my people, and I will be your God.” Isaiah 59:20–21 explains that this covenant is made possible by the Redeemer, and the reconciliation He offers will endure forever. This covenant does not guarantee the salvation of every Jew, but it does ensure that Israel as a nation will worship their Messiah. The Old Testament prophets who foretold this covenant, such as Isaiah, Jeremiah, Hosea, and Ezekiel, all proclaimed that it would be fulfilled in the future. Since their time, Israel has yet to be an independent nation that worships its Messiah (Romans 9–11). This will occur during the 1,000-year reign of Christ.
Other Promises
These are the covenants God made with IIsrael that are to be fulfilled in Jesus’ 1,000-year reign, but the Bible lists other promises that will be fulfilled, too. God promised Jesus He will make His enemies a footstool, and that Jesus’ followers will worship Him freely (Psalm 110). God promised the nations of the world that they would live in peace with Jesus as their ruler (Daniel 7:11-14). And He promised creation that the curse would be lifted (Romans 8:18-23), animals and the earth would be restored to peace and prosperity (Isaiah 11:6-9;32:13-15), and people would be freed from disease «I will seek that which was lost, and bring again that which was driven away, and will bind up that which was broken, and will strengthen that which was sick: but I will destroy the fat and the strong; I will feed them with judgment. », (Ezekiel 34:16). These, too, will be fulfilled during the 1,000-year reign.
The primary purpose of Jesus’ 1,000-year reign is to fulfill the prophecies given to Israel and the promises made to Jesus, the nations, and the entire earth. God’s covenants were voluntary and one-sided. He promised He would bless Israel and restore the world in specific ways, and He will.