Psalms 58:10 - Joseph Benson’s Commentary on the Old and New Testaments

The righteous shall rejoice when he seeth the vengeance The vengeance of God upon the enemies of his church. That is, he shall rejoice when he sees the blessed effects of it; the vindication of God's honour, and the deliverance of himself, and all good men. The pomp and power, the prosperity and success of the wicked, are often a discouragement to the righteous. It weakens their hands, and is sometimes a strong temptation to them to call in question the wisdom and equity of the dispensations of divine providence; but when they see the judgments of God taking away the wicked, and just vengeance taken on them, although but in part, for the mischief they have done to the people and cause of God, they rejoice in the satisfaction thereby given to their faith in God's providence, and in his justice and righteousness in governing the world. He shall wash his feet in the blood of the wicked There shall be so great a slaughter of his enemies, that he might, if he pleased, wash his feet in their blood. It is an allusion to a great conqueror, who, upon “returning with a complete victory from the slaughter of his enemies, dips his feet in their blood as he passes over their carcasses.” Bishop Patrick.