Albert Barnes Commentary Psalms 72:1

"Give the king thy judgments, O God, And thy righteousness unto the king`s son." — Psalms 72:1 (ASV)

Give the king - Supposing the psalm to have been composed by David in view of the inauguration of his son and successor, this is a prayer that God would bestow on him the qualifications which would tend to secure a just, a protracted, and a peaceful reign.

Though it is to be admitted that the psalm was designed to refer ultimately to the Messiah, and to be descriptive of his reign, yet there is no impropriety in supposing that the psalmist believed the reign of Solomon would be, in some proper sense, emblematic of that reign. It was his desire that the reign of the one might, as far as possible, resemble that of the other.

There is no improbability, therefore, in supposing that the mind of the psalmist might have been directed to both in the composition of the psalm, and that while he used the language of prayer for the one, his eye was mainly directed to the characteristics of the other.

Your judgments - Knowledge, authority, and the ability to execute your judgments, or your laws. That is, he speaks of the king as appointed to administer justice, to maintain the laws of God, and to exercise judicial power.

It is one of the primary ideas in the character of a king that he is the fountain of justice, the maker of the laws, and the dispenser of right to all his subjects. The officers of the law administer justice under him; the last appeal is to him.

And your righteousness - That is, clothe him, in the administration of justice, with a righteousness like your own. Let it be seen that he represents you; that his government may be regarded as your own administration through him.

To the king’s son - Not only to him, but to his successor; that is, let the administration of justice in the government be perpetuated. There is no improbability in supposing that in this the psalmist may have designed also to refer to the last and the greatest of his successors in the line—the Messiah.