Psalms 89:3

3 I have made a covenant with my chosen. The more effectually to confirm himself and all the godly in the faith of the Divine promise, he introduces God himself as speaking and sanctioning, by his authority, what had been said in the preceding verse. As faith ought to depend on the Divine promise, this manner of speaking, by which God is represented as coming forward and alluring us to himself by his own voice, is more forcible than if the prophet himself had simply stated the fact. And when God in this way anticipates us, we cannot be charged with rashness in coming familiarly to him; even as, on the contrary, without His word we have no ground to presume that he will be gracious to us, or to hope, at the mere suggestion of our own fancy, for what he has not promised. Moreover, the truth of the promise is rendered still more irrefragable, when God declares that he had made a covenant with his servant David, ratified by his own solemn oath. It having been customary in ancient times to engrave leagues and covenants on tables of brass, a metaphor is here used borrowed from this practice. God applies to David two titles of distinction, calling him both his chosen and his servant. Those who would refer the former appellation to Abraham do not sufficiently attend to the style of the Book of Psalms, in which it is quite common for one thing to be repeated twice. David is called the chosen of God, because God of his own good pleasure, and from no other cause, preferred him not only to the posterity of Saul, and many distinguished personages, but even to his own brethren. If, therefore, the cause or origin of this covenant is sought for, we must necessarily fall back upon the Divine election.

The name of servant, which follows immediately after, is not to be understood as implying that David by his services merited any thing at the hand of God. He is called God’s servant in respect of the royal dignity, into which he had not rashly thrust himself, having been invested with the government by God, and having undertaken it in obedience to his lawful call. When, however, we consider what the covenant summarily contains, we conclude that the prophet has not improperly applied it to his own use, and to the use of the whole people; for God did not enter into it with David individually, but had an eye to the whole body of the Church, which would exist from age to age. The sentence, I will establish thy throne for ever, is partly to be understood of Solomon, and the rest of David’s successors; but the prophet well knew that perpetuity or everlasting duration, in the strict and proper sense, could be verified only in Christ. In ordaining one man to be king, God assuredly did not have a respect to one house alone, while he forgot and neglected the people with whom he had before made his covenant in the person of Abraham; but he conferred the sovereign power upon David and his children, that they might rule for the common good of all the rest, until the throne might be truly established by the advent of Christ.