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)