15 “Your throne, O God, is for ever and ever”. Because God has “'blessed You' for ever,” on account of the “grace poured over Your lips.” Now the throne of the Jewish Kingdom was a temporal one; belonging to those who were under the Law, not to those who were under “grace:” He came to “redeem those who were under the Law,” and to place them under “Grace.” His “Throne is for ever and ever.” Why? For that first throne of the Kingdom was but a temporal one: whence then have we a “throne for ever and ever”? Because it is God's throne. O divine Attribute of Eternity! for God could not have a temporal throne. “Your throne, O God, is for ever and ever— a sceptre of direction is the sceptre of Your Kingdom.” “The sceptre of direction” is that which directs mankind: they were before crooked, distorted; they sought to reign for themselves: they loved themselves, loved their own evil deeds: they submitted not their own will to God; but would fain have bent God's will to conformity with their own lusts. For the sinner and the unrighteous man is generally angry with God, because it rains not! and yet would have God not be angry with himself, because he is profligate. And it is pretty much for this very reason that men daily sit, to dispute against God: “This is what He ought to have done: this He has not well done.” Thou forsooth see what you do. He knows not what He does! It is you that are crooked! His ways are right. When will you make the crooked coincide with the straight? It cannot be made to coincide with it. Just as if you were to place a crooked stick on a level pavement; it does not join on to it; it does not cohere; it does not fit into the pavement. The pavement is even in every part: but that is crooked; it does not fit into that which is level. The will of God then is “equal,” your own is “crooked:” it is because you can not be conformed unto it, that it seems “crooked” unto you: rule you yourself by it; seek not to bend it to your own will: for you can not accomplish it; that is at all times “straight”! Would you abide in Him? “Correct you yourself;” so will the sceptre of Him who rules you, be unto you “a rule of direction.” Thence is He also called King, from “ruling.” For that is no “ruler” that does not correct. Hereunto is our King a King of “right ones.” Just as He is a Priest (Sacerdos) by sanctifying us, so is He our King, our Ruler, by “ruling” us....
16. “You have loved righteousness, and hated iniquity”. See there “the rod of direction” described. “You have loved righteousness, and hated iniquity.” Draw near to that “rod;” let Christ be your King: let Him “rule” you with that rod, not crush you with it. For that rod is “a rod of iron;” an inflexible rod. “You shall rule them with a rod of iron: and break them in pieces like a potter's vessel.” Some He rules; others He “breaks in pieces:” He “rules” them that are spiritual: He “breaks in pieces” them that are carnal....Would He so loudly declare that He was about to smite you, if He wished to smite you? He is then holding back His hand from the punishment of your offenses; but do not thou hold back. Turn you yourself to the punishment of your offenses: for unpunished offenses cannot be: punishment therefore must be executed either by yourself, or by Him: do thou then plead guilty, that He may reprieve you. Consider an instance in that penitential Psalm: “Hide Your face from my sins.” Did he mean “from me”? No: for in another passage he says plainly, “Hide not Your face from me.” “Turn” then “Your face from my sins.” I would have You not see my sins. For God's “seeing” is animadverting upon. Hence too a Judge is said to “animadvert” on that which he punishes; i.e. to turn his mind on it, to bend it thereon, even to the punishment of it, inasmuch as he is the Judge. So too is God a Judge. “Turn Thou Your face from my sins.” But you yourself, if you would have God turn “His face” from them, turn not your own face from them. Observe how he proposes this to God in that very Psalm: “I acknowledge,” he says, “my transgression, and my sin is ever before me.” He would fain have that which he wishes to be ever before his own eyes, not be before God's eyes. Let no one flatter himself with fond hopes of God's mercy. His sceptre is “a sceptre of righteousness.” Do we say that God is not merciful? What can exceed His mercy, who shows such forbearance to sinners; who takes no account of the past in all that turn unto Him? So love thou Him for His mercy, as still to wish that He should be truthful. For mercy cannot strip Him of His attribute of justice: nor justice of that of mercy. Meanwhile during the time that He postpones your punishment, do not thou postpone it.
17. “Therefore, God, Your God, has anointed You.” It was for this reason that He anointed you, that you might love righteousness, and hate iniquity. And observe in what way he expresses himself. “Therefore, God, Your God, has anointed You:” i.e. “God has anointed You, O God.” “God” is “anointed” by God. For in the Latin it is thought to be the same case of the noun repeated: in the Greek however there is a most evident distinction; one being the name of the Person addressed; and one His who makes the address, saying, “God has anointed You.” “O God, Your God has anointed You,” just as if He were saying, “Therefore has Your God, O God, anointed You.” Take it in that sense, understand it in that sense; that such is the sense is most evident in the Greek. Who then is the God that is “anointed” by God? Let the Jews tell us; these Scriptures are common to us and them. It was God, who was anointed by God: you hear of an “Anointed” one; understand it to mean “Christ.” For the name of “Christ” comes from “chrism;” this name by which He is called “Christ” expresses “unction:” nor were kings and prophets anointed in any kingdom, in any other place, save in that kingdom where Christ was prophesied of, where He was anointed, and from whence the Name of Christ was to come. It is found nowhere else at all: in no one nation or kingdom. God, then, was anointed by God; with what oil was He anointed, but a spiritual one? For the visible oil is in the sign, the invisible oil is in the mystery; the spiritual oil is within. “God” then was “anointed” for us, and sent unto us; and God Himself was man, in order that He might be “anointed:” but He was man in such a way as to be God still. He was God in such a way as not to disdain to be man. “Very man and very God;” in nothing deceitful, in nothing false, as being everywhere true, everywhere “the Truth” itself. God then is man; and it was for this cause that “God” was “anointed,” because God was Man, and became “Christ.”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)