4 “What? Was He then other than now He is?” Away with the supposition. For what follows?
“You are Yourself my King and my God.”. “You are Yourself;” for You are not changed. I see that the times are changed; but the Creator of times is unchanged. “You are Yourself my King and my God.” You are wont to guide me: to govern me, to save me. “You who commandest salvation unto Jacob.” What is, “You who commandest”? Even though in Your own proper Substance and Nature, in which You are whatsoever You are, You were hid from them; and though You did not converse with the fathers in that which You are in Yourself, so that they could see You “face to face,” yet by any created being whatsoever “You command salvation unto Israel.” For that sight of You “face to face” is reserved for those set free in the Resurrection. And the very “fathers” of the New Testament too, although they saw Your mysteries revealed, although they preached the secret things so revealed to them, nevertheless said that they themselves saw but “in a glass, darkly,” but that “seeing face to face” is reserved to a future time, when what the Apostle himself speaks of shall have come. “When Christ our life shall appear, then shall you also appear with Him in glory.” It is against that time then that vision “face to face” is reserved for you, of which John also speaks: “Beloved, we are now the sons of God: and it does not yet appear what we shall be. We know that, when He shall appear, we shall be like Him; for we shall see Him as He is.” Although then at that time our fathers saw You not as You are, “face to face,” although that vision is reserved against the resurrection, yet, even though they were Angels who presented themselves, it is Thou, “Who commandest salvation unto Jacob.” You are not only present by Your own Self; but by whatsoever created being You appeared, it is Thou that dost “command” by them, that which You do by Your own Self in order to the salvation of Your servants: but that which they do whom Thou “commandest” it, is done to procure the salvation of Your servants. Since then You are Yourself “my King and my God, and You command salvation unto Jacob,” wherefore are we suffering these things?
Source: The Enarrations, or Expositions, on the Psalms (New Advent)