Right worship and everlasting authority are inseparable, as we learn from God’s covenant with David. The Lord removed David’s predecessor, Saul, from the throne of Israel when Saul acted rashly and did not worship God in the appointed manner (1 Sam. 13:8–15). Moreover, God confirmed His rejection of Saul when the king did not kill Agag as he was supposed to (chap. 15), thereby reflecting a heart not intent on worshiping the Lord. David, on the other hand, was made a party to an everlasting covenant with God on account of his commitment to the worship of Lord (2 Sam. 7:1–17). God promised that David would never fail to have a son on the throne of Israel, that his authority would be exercised forever.
In the Davidic covenant, we see the interplay of conditionality and unconditionality with respect to the kingship of Israel. Certainly God was not obligated to choose David’s line, nor was He obligated to grant him a perpetual reign over His people. This choice was by grace and guaranteed by the Lord’s gracious decision to swear an oath, as today’s passage indicates (Ps. 132:11). Yet, we also see conditional aspects of this covenant. Psalm 132:12 also tells us that the sons of David have to keep the Lord’s covenant regulations if they are to sit on the throne. The Davidic covenant is unconditional—David cannot fail to have a son on the throne—and yet it is also conditional—only the obedient son of David will sit on his throne forever.
This apparent paradox is resolved in Christ, the son of David according to the flesh (Rom. 1:1–4). Being the eternal second person of the Trinity, His reign is necessarily eternal. Yet Jesus also enjoyed exaltation as the God-man to an everlasting reign on David’s throne because of His perfect obedience to His Father’s commands (Phil. 2:5–11). As a man, Jesus kept the Lord’s covenant. Thus, we can be confident in the psalmist’s declaration that God’s chosen king will rule from Zion, and we will worship Him forever (vv. 13–18).
Until Christ returns, enemies will rebel against His rule, but their eventual defeat is sure (v. 18). John Calvin comments, “The . . . people of God will never enjoy such peace on earth as altogether to escape being assaulted by the variety of enemies which Satan stirs up for their destruction. It is enough to have it declared, upon divine authority, that their attempts shall be unsuccessful, and that they will retire eventually with ignominy and disgrace.”