1 “For Salomon” indeed this Psalm's title is fore-noted: but things are spoken of therein which could not apply to that Salomon king of Israel after the flesh, according to those things which holy Scripture speaks concerning him: but they can most pertinently apply to the Lord Christ. Whence it is perceived, that the very word Salomon is used in a figurative sense, so that in him Christ is to be taken. For Salomon is interpreted peace-maker: and on this account such a word to Him most truly and excellently does apply, through Whom, the Mediator, having received remission of sins, we that were enemies are reconciled to God. For “when we were enemies we were reconciled to God through the death of His Son.” The Same is Himself that Peace-maker....Since then we have found out the true Salomon, that is, the true Peace-maker: next let us observe what the Psalm does teach concerning Him.
2. “O God, Your judgment to the King give Thou, and Your justice to the King's Son”. The Lord Himself in the Gospel says, “The Father judges not any one, but all judgment He has given to the Son:” this is then, “O God, Your judgment to the King give Thou.” He that is King is also the Son of the King: because God the Father also is certainly King. Thus it has been written, that the King made a marriage for His Son. But after the manner of Scripture the same thing is repeated. For that which he has said in, “Your judgment;” the same he has otherwise expressed in, “Your justice:” and that which he has said in, “the King,” the same he has otherwise expressed in, “to the King's Son.”...But these repetitions do much commend the divine sayings, whether the same words, or whether in other words the same sense be repeated: and they are mostly found in the Psalms, and in the kind of discourse whereby the mind's affection is to be awakened.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)