Charles H. Spurgeon on Psalms 149:9

To execute upon them the judgment written. Israel as a nation had this to do, and did it, and then they rejoiced in the God who gave success to their arms. We praise our God after another fashion; we are not executioners of justice, but heralds of mercy. It would be a sad thing for any one to misuse this text: lest any warlike believer should be led to do so, we would remind him that the execution must not go beyond the sentence and warrant; and we have received no warrant of execution against our fellow men. Christians have no commission of vengeance; it is theirs to execute the command of mercy, and that alone. This honour have all his saints. All the godly shared in the triumphs of the Lord when he smote Israel's foes. We have like honour, but it is shown in victories of another sort. All the holy ones are sent upon errands by their holy Lord. The honours described in this Psalm are common to all the family of grace; and such service as the Lord appoints is to be undertaken by every one of them, without exception. The Lord honours all his chosen here, and he will glorify them all hereafter: this rule is without exception. Surely in this we have the best argument for glorifying the Lord, wherefore we close our new song with another Hallelujah, Praise ye the Lord.