David here speaks for himself in the first place, professing that his joy was in God's strength and in his salvation, and not in the strength or success of his armies. He also directs his subjects herein to rejoice with him, and to give God all the glory of the victories he had obtained; and all with an eye to Christ, of whose triumphs over the powers of darkness David's victories were but shadows. 1. They here congratulate the king on his joys and concur with him in them (Psa 21:1): "The king rejoices, he uses to rejoice in thy strength, and so do we; what pleases the king pleases us," Sa2 3:36. Happy the people the character of whose king it is that he makes God's strength his confidence and God's salvation his joy, that is pleased with all the advancements of God's kingdom and trusts God to bear him out in all he does for the service of it. Our Lord Jesus, in his great undertaking, relied upon help from heaven, and pleased himself with the prospect of that great salvation which he was thereby to work out. 2. They gave God all the praise of those things which were the matter of their king's rejoicing. (1.) That God had heard his prayers (Psa 21:2): Thou hast given him his heart's desire (and there is no prayer accepted but what is the heart's desire), the very thing they begged of God for him, Psa 20:4. Note, God's gracious returns of prayer do, in a special manner, require our humble returns of praise. When God gives to Christ the heathen for his inheritance, gives him to see his seed, and accepts his intercession for all believers, he give him his heart's desire. (2.) That God had surprised him with favours, and much outdone his expectations (Psa 21:3): Thou preventest him with the blessings of goodness. All our blessings are blessings of goodness, and are owing, not at all to any merit of ours, but purely and only to God's goodness. But the psalmist here reckons it in a special manner obliging that these blessings were given in a preventing way; this fixed his eye, enlarged his soul, and endeared his God, as one expresses it. When God's blessings come sooner and prove richer than we imagine, when they are given before we prayed for them, before we were ready for them, nay, when we feared the contrary, then it may be truly said that he prevented us with them. Nothing indeed prevented Christ, but to mankind never was any favour more preventing than our redemption by Christ and all the blessed fruits of his mediation. (3.) That God had advanced him to the highest honour and the most extensive power: "Thou hast set a crown of pure gold upon his head and kept it there, when his enemies attempted to throw it off." Note, Crowns are at God's disposal; no head wears them but God sets them there, whether in judgment to his land or for mercy the event will show. On the head of Christ God never set a crown of gold, but of thorns first, and then of glory. (4.) That God had assured him of the perpetuity of his kingdom, and therein had done more for him than he was able either to ask or think (Psa 21:4): "When he went forth upon a perilous expedition he asked his life of thee, which he then put into his hand, and thou not only gavest him that, but withal gavest him length of days for ever and ever, didst not only prolong his life far beyond his expectation, but didst assure him of a blessed immortality in a future state and of the continuance of his kingdom in the Messiah that should come of his loins." See how God's grants often exceed our petitions and hopes, and infer thence how rich he is in mercy to those that call upon him. See also and rejoice in the length of the days of Christ's kingdom. He was dead, indeed, that we might live through him; but he is alive, and lives for evermore, and of the increase of his government and peace there shall be no end; and because he thus lives we shall thus live also. (5.) That God had advanced him to the highest honour and dignity (Psa 21:5): "His glory is great, far transcending that of all the neighbouring princes, in the salvation thou hast wrought for him and by him." The glory which every good man is ambitious of is to see the salvation of the Lord. Honour and majesty hast thou laid upon him, as a burden which he must bear, as a charge which he must account for. Jesus Christ received from God the Father honour and glory (Pe2 1:17), the glory which he had with him before the worlds were, Joh 17:5. And on him is laid the charge of universal government and to him all power in heaven and earth is committed. (6.) That God had given him the satisfaction of being the channel of all bliss to mankind (Psa 21:6): "Thou hast set him to be blessings for ever" (so the margin reads it), "thou hast made him to be a universal blessing to the world, in whom the families of the earth are, and shall be blessed; and so thou hast made him exceedingly glad with the countenance thou hast given to his undertaking and to him in the prosecution of it." See how the spirit of prophecy gradually rises here to that which is peculiar to Christ, for none besides is blessed for ever, much less a blessing for ever to that eminency that the expression denotes: and of him it is said that God made him full of joy with his countenance.

In singing this we should rejoice in his joy and triumph in his exaltation.

The king shall joy in thy strength, O Lord,.... Either in that strength which is in Jehovah himself, in whom is everlasting strength; and which is seen in the works of creation and providence, and is the same in Christ himself, as he is the mighty God; or else in the strength which Jehovah communicated to Christ as man, whereby he was strengthened in his human nature to go through and complete the work of man's redemption; or in the strength which the Lord puts forth, and the power which he exerts towards and upon his people, in conversion; which is the produce of the exceeding greatness of his power; and in strengthening them, from time to time, to exercise grace, discharge duty, and withstand temptations and sin; and in keeping them safe to the end; in supporting them under all their trials, and in carrying on and finishing the work of faith upon their souls; all which is matter of joy to Christ;

and in thy salvation how greatly shall he rejoice? meaning either his own salvation by the Lord, from all his sorrows and troubles, and out of the hands of all enemies, being in the presence of God, where is fulness of joy, Psa 16:9; or else the salvation of his people by him, which Jehovah appointed them to, secured for them in the covenant of grace, sent Christ to work out for them, applies by his Spirit, and at last puts into the full possession of: Christ rejoices at the effectual calling and conversion of his people, when salvation is brought near unto them; and especially at their glorification, when they shall be in the full enjoyment of it; then will they be his joy, and crown of rejoicing: this is the joy that was set before him, which made him go so cheerfully through his sufferings and death for them, Heb 12:2; the reasons of this joy are, because of the great love he bears to them; the interest and property he has in them; his undertakings for them, as their surety, to bring them safe to glory; his purchase of them by his blood; his intercession for them, that they might be with him to behold his glory; and, last of all, because of his Father's glory, his own glory, and the glory of the blessed Spirit, which are concerned in the salvation of these persons.