Verse 1
Psalms 21:1. The king shall joy in thy strength — Conferred upon him, and put forth, by thee, on his behalf, against his enemies. Though by the king here we may understand King David, who composed this Psalm, yet it may be much better explained of the King Messiah; understood of whom, the words thy strength mean the divine power, which was manifested in the resurrection of Christ, and in the establishment of his gospel.

Verse 2
Psalms 21:2. Thou hast given him his heart’s desire — Thou hast granted all that he desired in his heart, as well as that which he openly requested with his lips. “The desire of Christ’s heart was his own resurrection and exaltation, for the benefit of his church; and now he ever liveth to make request with his lips, for the conversion and salvation of sinners. Such desires will be granted, and such requests will never be withholden. Let us be careful to frame ours after that all-perfect model of divine love.” — Horne.

Verse 3
Psalms 21:3. Thou preventest him — Or, didst prevent him, namely, David; crowning him with manifold blessings, both more and sooner than he desired or expected, surprising him with the gift of the kingdom, and with many happy successes. With the blessings of goodness — That is, with excellent blessings, or with abundance of good. Applying this to Christ, we must say, The Son of God could not be more ready to ask for the blessings of the divine goodness than the Father was to give them, and his disposition is the same toward all his adopted sons. By the crown of pure gold, may be meant, in general, an illustrious crown, which is here represented as being set upon our Lord’s head at his exaltation into heaven, in token of his being then advanced to this chief exercise of his regal authority. Thus he is said, Psalms 8:5, to be crowned with glory and honour; and St. John says, with respect to his deified humanity, in which he was made King of kings, and Lord of lords, that on his head were many crowns, Revelation 19:12; Revelation 19:16.

Verse 4
Psalms 21:4. He asked life of thee — Applied to David it means, He asked only the preservation of his short and mortal life, which was often exposed to the utmost perils. And thou gavest him length of days for ever and ever — Thou gavest him a long life and reign here, and after that didst translate him to live with thee for ever. But this was far more eminently fulfilled in Christ, who asked of his Father life, or to be saved from death, (Hebrews 5:7,) though with submission to his will: but his Father, though he saw it necessary to take away his temporal life, yet instantly gave him another, and that far more noble, instead of it, even the perfect possession of an everlasting and most glorious life, both in his soul and body, at his right hand.

Verse 5
Psalms 21:5. His glory — His fame or renown, is great in thy salvation — By reason of those great and glorious deliverances which thou hast wrought both for him and by him. Honour and majesty hast thou laid upon him — Or, fitted to him, or upon him, or made adequate to him, as the word תשׁוה, teshav-veh, signifies. Thou hast given him honour and power suitable to his glorious person and high endowments. “What tongue,” says Dr. Horne, “can express the ‘glory, honour, and majesty,’ with which the King of righteousness and peace was invested upon his ascension, when he took possession of the throne prepared for him, and received the homage of heaven and earth! The sacred imagery in St. John’s Revelation sets them before our eyes in such a manner, that no one can read the description whose heart will not burn within him, through impatient desire to behold them.” See Revelation, chapters 4., 7., 19., 21., 22.

Verse 6
Psalms 21:6. Thou hast made him blessed for ever — Hebrew, תשׁיתהו ברכות, teshitheehu berachoth, Thou hast set him to be blessings for ever; that is, to be the author of all felicity to his subjects and servants: see Galatians 3:8, where we learn, that Christ, by his death and passion, having removed the curse, became the fountain of all blessedness to his people, in time and in eternity; being himself the blessing promised to Abraham, and the chief subject of the patriarchal benedictions. Thou hast made him exceeding glad — Thus Christ says of himself, Psalms 16:9-11, My heart is glad, and my glory rejoices; in thy presence is fulness of joy, &c., and the psalmist says of him, Psalms 45:7, Thy God hath anointed thee with the oil of gladness above thy fellows.

Verse 7
Psalms 21:7. For the king trusteth in the Lord — Confides in him, who never fails to perform his promises; and through the mercy of the Most High, &c. — Through his kindness who is superior to all other beings, and has all events in his hands and under his control; he shall not be moved — The throne of David, and of his seed the Messiah, shall stand fast, though all the powers on earth should combine to overturn it. “The throne of Christ, as man,” says Dr. Horne, “was erected and established by his trust and confidence in the Father during his humiliation and passion. Faith in God, therefore, is the way that leadeth to honour and stability.”

Verse 8-9
Psalms 21:8-9. Thy hand shall find out all thine enemies — When they seek to hide themselves, or flee away from thee, thy hand shall discover, overtake, and destroy them. Thou shalt make them as a fiery oven — Hebrew, תשׁיתמו כתנור אשׁ, teshithemo chetannur esh, thou shalt put them, as it were, into an oven of fire. The Lord shall swallow them up — Destroy them. Thus, Psalms 2:9, Thou shalt bruise them with a rod of iron, &c., which prediction, and those contained in these verses, particularly relate to the unbelieving Jews. Compare Malachi 4:1; Psalms 2:2-4; Psalms 109:13-15.

Verse 10-11
Psalms 21:10-11. Their fruit shalt thou destroy — Their children. God will take away both root and branch; the parents and all that wicked race. For they intended evil against thee — That is, against God; not directly, but by consequence, because it was against David, whom God had anointed, or against the Messiah, of whom he was a type, and against the Lord’s people, injuries done to whom, God takes to be done to himself, Zechariah 2:8. They imagined a mischievous device, which they are not able to perform — This clause seems to be added to teach us this great and necessary lesson, that men are justly punished by God for their wicked intentions, although they be hindered from the execution of them, contrary to what some Jewish doctors, and others, have taught. “Vengeance came upon the Jews to the uttermost, because of their intended malice against Christ. They, like Joseph’s brethren, thought evil against him, but they were not able to perform it, for God meant it unto good, to bring it to pass, as it is this day, to save much people alive, Genesis 50:20. So let all the designs of ungodly men against thy church, O Lord, through thy power of bringing good out of evil, turn to her advantage; and let all men be convinced that no weapon formed against thee can prosper.”

Verse 12
Psalms 21:12. Therefore shalt thou make them turn their back — That is, flee away at the first sight of thee. Or, thou shalt set them as a butt to shoot at, as the like phrase is used Job 7:20; Job 16:12. When thou shalt make ready thine arrows, &c., against the face of them — Or, against them, the word face being often redundant. “The judgments of God are called his arrows, being sharp, swift, sure, and deadly. What a dreadful situation, to be set as a mark and butt, at which these arrows are directed! View Jerusalem compassed by the Roman armies without, and torn to pieces by the animosity of desperate and bloody factions within. No further commentary is requisite upon this verse. Tremble and repent, is the inference to be drawn by every Christian community under heaven, in which appear the symptoms of degeneracy and apostacy.” — Horne.