The Millenium or the 1000 year reign of Christ, is the ultimate fulfillment of several covenants God made with individuals and Israel.
Make a joyful noise unto the LORD, all ye lands. Serve the LORD with gladness: come before his presence with singing. Know ye that the LORD he is God: it is he that hath made us, and not we ourselves; we are his people, and the sheep of his pasture. ~ Psalm 100:1-3