Commentary on the Bible, by Adam Clarke, [1831], at sacred-texts.com
The psalmist returns thanks to God for giving him the victory over his enemies; which victory he had earnestly requested, Psa 21:1, Psa 21:2. He enters into a detail of the blessings that in consequent of the victory he had obtained, Psa 21:3-7. He predicts the destruction of all those who may hereafter rise up against him, Psa 21:8-12; and concludes with praising the power of Jehovah, Psa 21:13.
In the title of this Psalm there is nothing particularly worthy of remark. The occasion of it is variously understood. Some think it was composed to celebrate the victory obtained over Sennacherib; others, that it was made on the recovery of Hezekiah, and the grant of fifteen years of longer life; see Psa 21:4. Others and they with most appearance of propriety consider it a song of rejoicing composed by David for his victory over the Ammonites which ended in the capture of the royal city of Rabbah, the crown of whose king David put on his own head, see Psa 21:3, and to procure which victory David offered the prayers and sacrifices mentioned in the preceding Psalm. Lastly, many think that it is to be wholly referred to the victories of the Messiah; and it must be owned that there are several expressions in it which apply better to our Lord than to David, or to any other person; and to him the Targum applies it, as does likewise my old Anglo-Scottish Psalter in paraphrasing the text.
The king shall joy - מלך משיחא melech Meshicha, "the King Messiah." - Targum. What a difference between ancient and modern heroes! The former acknowledged all to be of God, because they took care to have their quarrel rightly founded; the latter sing a Te Deum, pro forma, because they well know that their battle is not of the Lord. Their own vicious conduct sufficiently proves that they looked no higher than the arm of human strength. God suffers such for a time, but in the end he confounds and brings them to naught.
Thou hast given him his heart's desire - This seems to refer to the prayers offered in the preceding Psalm; see especially Psa 21:1-4.
Thou preventest him - To prevent, from prcevenio, literally signifies to go before. Hence that prayer in the communion service of our public Liturgy, "Prevent us, O Lord, in all our doings, with thy most gracious favor!" That is, "Go before us in thy mercy, make our way plain, and enable us to perform what is right in thy sight!" And this sense of prevent is a literal version of the original word תקדמנו tekademennu. "For thou shalt go before him with the blessings of goodness."
Our ancestors used God before in this sense. So in Henry V.'s speech to the French herald previously to the battle of Agincourt: -
"Go therefore; tell thy master, here I am.
My ransom is this frail and worthless trunk;
My army, but a weak and sickly guard:
Yet, God before, tell him we will come on,
Though France himself, and such another neighbor,
Stand in our way."
A crown of pure gold - Probably alluding to the crown of the king of Rabbah, which, on the taking of the city, David took and put on his own head. See the history, Sa2 12:26-30 (note).
He asked life of thee - This verse has caused some interpreters to understand the Psalm of Hezekiah's sickness, recovery, and the promised addition to his life of fifteen years; but it may be more literally understood of the Messiah, of whom David was the type, and in several respects the representative.
His glory is great - But great as his glory was, it had its greatness from God's salvation. There is no true nobility but of the soul, and the soul has none but what it receives from the grace and salvation of God.
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.
The king trusteth in the Lord - It was not by my skill or valor that I have gained this victory, but by faith in the strong protecting, and conquering arm of Jehovah.
He shall not be moved - Perhaps this may be best understood of him who was David's prototype. His throne, kingdom, and government, shall remain for ever.
Thine hand shall find out - Thy uncontrollable power shall find out all thine enemies, wheresoever hidden or howsoever secret. God knows the secret sinner, and where the workers of iniquity hide themselves.
Thou shalt make them as a fiery oven - By thy wrath they shall be burnt up, and they shall be the means of consuming others. One class of sinners shall, in God's judgments, be the means of destroying another class; and at last themselves shall be destroyed.
Their fruit shalt thou destroy - Even their posterity shall be cut off, and thus their memorial shall perish.
For they intended evil - Sinners shall not be permitted to do all that is in their power against the godly; much less shall they be able to perform all that they wish.
Therefore shalt thou make them turn their back - God can in a moment strike the most powerful and numerous army, even in the moment of victory, with panic; and then even the lame, the army which they had nearly routed, shall take the prey, and divide the spoil.
Against the face of them - Thou shalt cause them to turn their backs and fly, as if a volley of arrows had been discharged in their faces. This seems to be the sense of this difficult verse.
Be thou exalted - Exalt thyself. O Lord - thy creatures cannot exalt thee. Lift thyself up, and discomfit thy foes by thine own strength! Thou canst give a victory to thy people over the most formidable enemies, though they strike not one blow in their own defense. God's right hand has often given the victory to his followers, while they stood still to see the salvation of God. How little can the strength of man avail when the Lord raiseth up himself to the battle! His children, therefore, may safely trust in him, for the name of the Lord is a strong tower; the righteous flee into it, and are safe.
Praise thy power - God is to receive praise in reference to that attribute which he has exhibited most in the defense or salvation of his followers. Sometimes he manifests his power, his mercy, his wisdom, his longsuffering, his fatherly care, his good providence, his holiness, his justice, his truth, etc. Whatever attribute or perfection he exhibits most, that should be the chief subject of his children's praise. One wants teaching, prays for it, and is deeply instructed: he will naturally celebrate the wisdom of God. Another feels himself beset with the most powerful adversaries, with the weakest of whom he is not able to cope: he cries to the Almighty God for strength; he is heard, and strengthened with strength in his soul. He therefore will naturally magnify the all-conquering power of the Lord. Another feels himself lost, condemned, on the brink of hell; he calls for mercy, is heard and saved: mercy, therefore, will be the chief subject of his praise, and the burden of his song.
The old Anglo-Scottish Psalter says, We sal make knowen thi wordes in gude wil and gude werk, for he synges well that wirkes well. For thi, sais he twise, we sal syng; ane tyme for the luf of hert; another, for the schewyng of ryghtwisness, til ensampil.