The covenant of David is God’s promise that one of David’s sons would always be on Israel’s throne. “And your house and your kingdom shall be established forever before you. Your throne shall be established forever”, 2 Samuel 7:16. For many centuries descendants of David did rule over Israel, but this stopped temporarily when the Gentile nations conquered Israel. (Then Israel had no independent government.)
Before Jesus was born, Mary, a descendant of David, was told “He (Jesus) shall be great, and shall be called the Son of the Highest: and the Lord God shall give unto him (Jesus) the throne of his father David: And he shall reign over the house of Jacob forever; and of his kingdom there shall be no end.” (Luke 1:32, 33) Jesus will reign forever so the everlasting covenant with David will be accomplished.
As the heir of the Davidic Covenant, Paul explains that Jesus will be “the mediator of the new covenant,” Hebrews 12:24. Hebrews 8:6 affirms Jesus as the mediator “of a better covenant which was established upon better promises.” This is in contrast to the original law covenant with Moses as the mediator.
This better, and blessed covenant will be established in the future. “For this is the covenant that I will make with the house of Israel after those days (after Armageddon), saith the Lord; I will put my laws into their mind, and write them in their hearts: and I will be to them a God, and they shall be to me a people:…all shall know me, from the least to the greatest. For I will be merciful to their unrighteousness, and their sins and their iniquities will I remember no more.” Hebrews 8:10-12.
Under this New Covenant, Jesus will rule in justice, wisdom, and love. Isaiah 9:6,7 “For unto us a child is born, unto us a son is given: and the government shall be upon his shoulder: and his name shall be called Wonderful, Counsellor, The mighty God, The everlasting Father, The Prince of Peace (these various rolls will work together to accomplish) of the increase of his government and peace there shall be no end, upon the throne of David, and upon his kingdom, to order it, and to establish it with judgment and with justice from henceforth even forever. The zeal of the LORD of hosts will perform this.”
Jesus holds the central figure in God’s plan to restore mankind to the perfection lost when Adam sinned. (See Acts 3:19-21.) Thus, He is both a descendant of David and will become the wonderful mediator of the New Covenant.