1....Our Lord Jesus Christ speaks in the Prophets, sometimes in His own Name, sometimes in ours, because He makes Himself one with us; as it is said, “they two shall be one flesh.” Wherefore also the Lord says in the Gospel, speaking of marriage, “therefore they are no more two, but one flesh.” One flesh, because of our mortality He took flesh; not one divinity, for He is the Creator, we the creature. Whatsoever then our Lord speaks in the person of the Flesh He took upon Him, belongs both to that Head which has already ascended into heaven, and to those members which still toil in their earthly wandering. Let us hear then our Lord Jesus Christ speaking in prophecy. For the Psalms were sung long before the Lord was born of Mary, yet not before He was Lord: for from everlasting He was the Creator of all things, but in time He was born of His creature. Let us believe that Godhead, and, so far as we can, understand Him to be equal to the Father. But that Godhead equal to the Father was made partaker of our mortal nature, not of His own store, but of ours; that we too might be made partakers of His Divine Nature, not of our store, but of His.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)