Psalms 72:4

4. He shall judge the poor of the people. The poet continues his description of the end and fruit of a righteous government, and unfolds at greater length what he had briefly touched upon concerning the afflicted among the people. But it is a truth which ought to be borne in mind, that kings can keep themselves within the bounds of justice and equity only by the grace of God; for when they are not governed by the Spirit of righteousness proceeding from heaven, their government is converted into a system of tyranny and robbery. As God had promised to extend his care to the poor and afflicted among his people, David, as an argument to enforce the prayer which he presents in behalf of the king, shows that the granting of it will tend to the comfort of the poor. God is indeed no respecter of persons; but it is not without cause that God takes a more special care of the poor than of others, since they are most exposed to injuries and violence. Let laws and the administration of justice be taken away, and the consequence will be, that the more powerful a man is, he will be the more able to oppress his poor brethren. David, therefore, particularly mentions that the king will be the defender of those who can only be safe under the protection of the magistrate, and declares that he will be their avenger when they are made the victims of injustice and wrong. The phrase, The children of the afflicted, is put for the afflicted, an idiom quite common in Hebrew, and a similar form of expression is sometimes used by the Greeks, as when they say υἱους ἰατρων, the sons of physicians, for physicians. But as the king cannot discharge the duty of succouring and defending the poor which David imposes upon him, unless he curb the wicked by authority and the power of the sword, it is very justly added in the end of the verse, that when righteousness reigns, oppressors or extortioners will be broken in pieces. It would be foolish to wait till they should give place of their own accord. They must be repressed by the sword, that their audacity and wickedness may be prevented from proceeding to greater lengths. It is therefore requisite for a king to be a man of wisdom, and resolutely prepared effectually to restrain the violent and injurious, that the rights of the meek and orderly may be preserved unimpaired. Thus none will be fit for governing a people but he who has learned to be rigorous when the case requires. Licentiousness must necessarily prevail under an effeminate and inactive sovereign, or even under one who is of a disposition too gentle and forbearing. There is much truth in the old saying, that it is worse to live under a prince through whose lenity everything is lawful, than under a tyrant where there is no liberty at all.