Verses 1-3
Psalms 149:1-3. Sing unto the Lord a new song — For these new mercies conferred upon us, denied to former times. Let Israel rejoice in him that made him — That made them not only his creatures, but, which is unspeakably greater, his people; or, that advanced them to, and adorned them with, singular privileges, as the word עשׁה, here used, is understood 1 Samuel 12:6, and elsewhere. Let the children of Zion be joyful in their king — In Jehovah, who condescends, in a peculiar sense, to become their king, and, in the exercise of his kingly power, delivers, protects, and governs them as his subjects. Let them praise his name in the dance, &c. — According to the usage of that time and dispensation: see notes on Exodus 15:20-21; 2 Samuel 6:14. True Christians are now the people to whom belong the names and characters of saints, Israel, and children of Zion. They sing this holy song as the psalmist hath enjoined them to do. They sing it as new men, with new affections and dispositions, and in its evangelical sense, celebrating new victories, and victories of a new kind, and new and greater mercies, even a spiritual salvation and an eternal redemption. “They rejoice with hearts and voices,” if not also with “instruments, and every other token of joy, in him who made them, who created them anew in righteousness and true holiness: they are joyful in their king, who hath himself overcome, and is now leading them on to final conquest and triumph, to honour and immortality.”

Verse 4
Psalms 149:4. The Lord taketh pleasure in his people — He loveth them above all people, and rejoiceth over them to do them good. He will beautify the meek — The humble, and lowly, and contrite in heart, that tremble at his word, and submit to it; that are patient under their afflictions, and show all meekness toward all men. These the men of the world vilify and asperse; but God will justify them, and wipe off their reproach; nay, he will beautify, or adorn, or glorify them, as יפאר signifies. They shall appear, not only clear, but comely and honourable before all the world, with the comeliness and dignity wherewith he clothes them. He will beautify them with salvation, perhaps with temporal salvation, working remarkable deliverances for them; and then they who had lain among the pots, become as the wings of a dove covered with silver, Psalms 68:13 : but especially with eternal salvation. The righteous shall be beautified indeed in that day when they shine forth as the sun in the kingdom of their Father.

Verses 5-8
Psalms 149:5-8. Let the saints be joyful in glory — For the honour which God puts upon them. Let them sing aloud upon their beds — By night as well as by day, in the time usually devoted to rest and sleep, which they shall borrow to praise God in for his eminent and extraordinary blessings. Let the high praises of God be in their mouths; &c. — “In assured hopes of victory they shall go to war with psalms and hymns in their mouths, concerning the great acts of the Lord, which they shall courageously sing with a loud voice when they shall fall upon their enemies, and prefer to the two-edged sword which they carry in their hands.” — Bishop Patrick. To execute vengeance upon the heathen — For all their cruelties and injuries toward God’s people. This was literally accomplished by David upon the Philistines, Ammonites, Syrians, and other neighbouring nations. Their kings and nobles were taken prisoners, (Psalms 149:8,) and on some of them the judgment written (Psalms 149:9) was executed, as by Joshua on the kings of Canaan, by Gideon on the princes of Midian, and by Samuel on Agag. Jehoshaphat’s army had, at the same time, the high praises of God in their mouths, and a two-edged sword in their hand; for they went forth to war singing the praises of God, and then their sword did execution, 2 Chronicles 20:23. It may be applied to the time of the Maccabees, when the Jews sometimes gained great advantages against their oppressors. And it is evident from many passages both of the Old and New Testaments, especially from Zechariah 9:13-16; and Zechariah 14:17-19; Revelation 19:11-21, that something of a similar nature will take place when the antichristian powers are destroyed, and more glorious times are introduced.

Verse 9
Psalms 149:9. To execute upon them the judgment written — Appointed and declared in the Holy Scriptures. This is added to show that they do not do this work to satisfy any malicious or revengeful inclinations of their own, but in obedience to God’s command, and only in such a manner as he hath allowed in his word. They act by commission from him, and according to his direction. Thus the kings of the earth that shall be employed in the destruction of the New Testament Babylon, will only execute the judgment written, Revelation 17:16-17. But since now no such special commissions can be produced, this will by no means justify the violence either of subjects against their princes, or of princes upon their subjects, or of both upon their neighbours, under pretence of religion; for Christ never intended that his gospel should be propagated by fire and sword, or his righteousness wrought by the wrath of man. When the high praises of God are in our mouths, with them we should have an olive branch of peace in our hands. This honour have all his saints — For whose sakes God appoints these judgments to be executed. The reader will observe, however, that the complete accomplishment of this prophetical exhibition will not take place till the judgment of the great day, when the Lord shall come with ten thousand of his saints, to execute judgment upon all the ungodly, Jude, Jude 1:15; especially upon all who have rejected or apostatized, from the gospel of the grace of God. Kings and nobles that cast away the bands and cords of Christ’s government shall not then be able to cast away the fetters and chains of his justice and wrath. Then the judgment written shall be awfully executed, and indignation and wrath, tribulation and anguish, shall be the portion of those who did not obey the truth, but obeyed unrighteousness; and then shall all the saints have the honour of being assessors with Christ in judging the world, and beholding the degradation and punishment of their once insulting persecutors, who will be cut asunder with the two-edged sword, and slain before them, Luke 19:27.