Psalms 58:10

10The righteous shall rejoice when he seeth the vengeance It might appear at first sight that the feeling here attributed to the righteous is far from being consistent with the mercy which ought to characterise them; but we must remember, as I have often observed elsewhere, that the affection which David means to impute to them is one of a pure and well-regulated kind; and in this case there is nothing absurd in supposing that believers, under the influence and guidance of the Holy Ghost, should rejoice in witnessing the execution of divine judgments. That cruel satisfaction which too many feel when they see their enemies destroyed, is the result of the unholy passions of hatred, anger, or impatience, inducing an inordinate desire of revenge. So far as corruption is suffered to operate in this manner, there can be no right or acceptable exercise. On the other hand, when one is led by a holy zeal to sympathise with the justness of that vengeance which God may have inflicted, his joy will be as pure in beholding the retribution of the wicked, as his desire for their conversion and salvation was strong and unfeigned. God is not prevented by his mercy from manifesting, upon fit occasions, the severity of the judge, when means have been tried in vain to bring the sinner to repentance, nor can such an exercise of severity be considered as impugning his clemency; and, in a similar way, the righteous would anxiously desire the conversion of their enemies, and evince much patience under injury, with a view to reclaim them to the way of salvation: but when wilful obstinacy has at last brought round the hour of retribution, it is only natural that they should rejoice to see it inflicted, as proving the interest which God feels in their personal safety. It grieves them when God at any time seems to connive at the persecutions of their enemies; and how then can they fail to feel satisfaction when he awards deserved punishment to the transgressor?