How do we know God made an everlasting covenant with David?

David's assurance of an everlasting covenant comes from God's faithfulness, which is reiterated throughout Scripture. In 2 Samuel 23:5, David describes the covenant as 'ordered in all things and sure,' emphasizing that it doesn't depend on his performance but on God's unchanging promise. The New Testament reinforces this in Hebrews, where it speaks of Jesus as the mediator of a new covenant (Hebrews 9:15). This gives us assurance that God's plans for our salvation are certain and reliable, affirming our hope despite personal and circumstantial failures, as illustrated in David's life.