For thou hast set him to be blessings for ever. Some explain these words simply thus, That God had chosen David to be king, in order to pour upon him his blessings in rich abundance. But it is evident that something more is intended by this manner of speaking. It implies, that the king had such an exuberant abundance of all good things, that he might justly be regarded as a pattern of the greatness of the divine beneficence; or that, in praying, his name would be generally used to serve as an example of how the suppliant wished to be dealt with. The Jews were accustomed to speak of those being set to be a curse, who were rendered so detestable, and on whom the dreadful vengeance of God had been inflicted with such severity, that their very names served for cursing and direful imprecations. On the other hand, they were accustomed to speak of those being set to be a blessing, whose names we propose in our prayers as an example of how we desire to be blessed; as if a man for instance should say, May God graciously bestow upon thee the same favor which he vouchsafed to his servant David! I do not reject this interpretation, but I am satisfied with the other, which views the words as implying that the king, abounding in all kind of good things, was an illustrious pattern of the liberality of God. We must carefully mark what is said immediately after concerning joy: Thou hast gladdened him with joy before thy countenance [1] The people not only mean that God did good to the king, seeing he looked upon him with a benignant and fatherly eye, but they also point out the proper cause of this joy, telling us that it proceeded from the knowledge which the king had of his being the object of the Divine favor. It would not be enough for God to take care of us, and to provide for our necessities, unless, on the other hand, he irradiated us with the light of his gracious and reconciled countenance, and made us to taste of his goodness, as we have seen in the 4th Psalm, "There be many that say, Who will show us any good? Lord, lift thou up the light of thy countenance upon us, and we shall be saved." And without all doubt, it is true and solid happiness to experience that God is so favorable to us that we dwell as it were in his presence.

Footnotes

1 - Walford reads this clause -- "Thou hast made him glad with the joy of thy presence."

For thou hast made him most blessed for ever - Margin, as in Hebrew, "set him" to be "blessings." The expression in our translation, as it is now commonly understood, would mean that God had made him "happy" or "prosperous." This does not seem to be the sense of the original. The idea is, that he had made him a blessing to mankind or to the world; or, that he had made him to be a source of blessing to others. Blessings would descend through him; and though in the consciousness of this fact he would be "happy," and in that sense be "blessed," yet the idea is rather that blessings would be imparted or scattered through him. Blessings would abound to others through his own reign; blessings through the reigns of those who should succeed him in the throne; blessings would be imparted to men as far as the import of the promise extended, that is, forever, Psalm 21:4. The word "forever" here undoubtedly, as it was used by the Spirit of inspiration, was designed to refer to the eternal blessings which would descend on mankind through the Messiah, the illustrious descendant of David. How far David himself understood this, is not material inquiry. He was undoubtedly directed by the Spirit of inspiration to use such language as would fairly and properly express this. It is right, therefore, for us so to regard it, and so to interpret and apply it.
Thou hast made him exceeding glad - Margin, as in Hebrew, "gladded him with joy." The Hebrew phrase means, as it is expressed in our translation, that he had been made very glad, or very happy. The favors of God to him, alike in his protection and in the promises which had been made in reference to the future, were such as to make him happy in the highest degree.
With thy countenance - With thy favor. By lifting the light of thy countenance upon him; or, as we should express it, by "smiling" upon him. See the notes at Psalm 4:6.

Thou hast made him most blessed for ever - Literally, "Thou hast set him for blessings for ever." Thou hast made the Messiah the Source whence all blessings for time and for eternity shall be derived. He is the Mediator between God and man.
Thou hast made him exceeding glad - Jesus, as Messiah, for the joy that was set before him, of redeeming a lost world by his death, endured the cross, and despised the shame, and is for ever set down on the right hand of God.

For thou hast made him most (d) blessed for ever: thou hast made him exceeding glad with thy countenance.
(d) You have made him your blessings to others, and a perpetual example of your favour forever.

For thou hast made him most blessed for ever,.... Not as God, for as such he is over all blessed for ever, and not made so; but as man and Mediator; the words may be rendered, "thou hast set him to be blessings for ever" (z); which design the blessings which are laid up in Christ for his people, and which he imparts unto, them, and they are blessed with in him; so that he is made a blessing, or rather blessings to them; such as redemption to free them from, bondage, righteousness to justify them, sanctification to make them holy, wisdom to direct and guide them, and strength to assist and support them; through whom they have the forgiveness of sins, by whom they have peace with God, and from whom they receive all their joy and comfort, and at last eternal life and happiness; and all these are for ever, they are irreversible blessings, are never repented of, nor taken away: or this blessedness may be understood of that which Christ himself enjoys as man; which lies in his human nature being exalted to union with the Son of God; in being heard and helped in the day of salvation; in being raised from the dead, and glory given him; in being set at God's right hand, angels, authorities, and powers, being subject to him; and in seeing the travail of his soul with satisfaction: the particular instance of his blessedness follows;
thou hast made him exceeding glad with thy countenance; the glorious presence of God in heaven; Christ having done his work on earth ascended to heaven, where he was received by his Father with a cheerful countenance, was made to sit down on the same throne with him, being well pleased with his obedience, righteousness, and sacrifice; and being now in the presence of God, in which is fulness of joy, and at his right hand, where are pleasures for evermore, the human nature of Christ is filled with an excess of joy; the words may be rendered, "thou hast made" or "wilt make him glad with joy (a), with thy countenance"; see Psalm 16:11.
(z) "posuisti vel pones eum benedictiones", Pagninus, Montanus, Vatablus; so Ainsworth, Cocceius, Gejerus. (a) "laetificabis eum in laetitia", Pagninus, Montanus, Michaelis; so Junius & Tremellius, Gejerus.

made him most blessed--or set him "to be blessings," as Abraham (Genesis 12:2).
with thy countenance--by sight of thee (Psalm 16:11), or by Thy favor expressed by the light of Thy countenance (Numbers 6:25), or both.

Countenance - Smiling upon him, by thy grace and favour.