1 The words, “I slept, and took rest; and rose, for the Lord will take me up,” lead us to believe that this Psalm is to be understood as in the Person of Christ; for they sound more applicable to the Passion and Resurrection of our Lord, than to that history in which David's flight is described from the face of his rebellious son. And, since it is written of Christ's disciples, “The sons of the bridegroom fast not as long as the bridegroom is with them;” it is no wonder if by his undutiful son be here meant that undutiful disciple who betrayed Him. From whose face although it may be understood historically that He fled, when on his departure He withdrew with the rest to the mountain; yet in a spiritual sense, when the Son of God, that is the Power and Wisdom of God, abandoned the mind of Judas; when the Devil wholly occupied him; as it is written, “The Devil entered into his heart,” may it be well understood that Christ fled from his face; not that Christ gave place to the Devil, but that on Christ's departure the Devil took possession. Which departure, I suppose, is called a flight in this Psalm, because of its quickness; which is indicated also by the word of our Lord, saying, “That you do, do quickly.” So even in common conversation we say of anything that does not come to mind, it has fled from me; and of a man of much learning we say, nothing flies from him. Wherefore truth fled from the mind of Judas, when it ceased to enlighten him. But Absalom, as some interpret, in the Latin tongue signifies, Patris pax, a father's peace. And it may seem strange, whether in the history of the kings, when Absalom carried on war against his father; or in the history of the New Testament, when Judas was the betrayer of our Lord; how “father's peace” can be understood. But both in the former place they who read carefully, see that David in that war was at peace with his son, who even with sore grief lamented his death, saying, “O Absalom, my son, would God I had died for you!” And in the history of the New Testament by that so great and so wonderful forbearance of our Lord; in that He bore so long with him as if good, when He was not ignorant of his thoughts; in that He admitted him to the Supper in which He committed and delivered to His disciples the figure of His Body and Blood; finally, in that He received the kiss of peace at the very time of His betrayal; it is easily understood how Christ showed peace to His betrayer, although he was laid waste by the intestine war of so abominable a device. And therefore is Absalom called “father's peace,” because his father had the peace, which he had not.
2. “O Lord, how are they multiplied that trouble me!”. So multiplied indeed were they, that one even from the number of His disciples was not wanting, who was added to the number of His persecutors. “Many rise up against me; many say unto my soul, There is no salvation for him in his God”. It is clear that if they had had any idea that He would rise again, assuredly they would not have slain Him. To this end are those speeches, “Let Him come down from the cross, if He be the Son of God;” and again, “He saved others, Himself He cannot save.” Therefore, neither would Judas have betrayed Him, if he had not been of the number of those who despised Christ, saying, “There is no salvation for Him in His God.”
3. “But You, O Lord, art my taker.” It is said to God in the nature of man, for the taking of man is, the Word made Flesh. “My glory.” Even He calls God his glory, whom the Word of God so took, that God became one with Him. Let the proud learn, who unwillingly hear, when it is said to them, “For what have you that you did not receive? Now if you received it, why do you glory as if you had not received it?” “And the lifter up of my head”. I think that this should be here taken of the human mind, which is not unreasonably called the head of the soul; which so inhered in, and in a sort coalesced with, the supereminent excellency of the Word taking man, that it was not laid aside by so great humiliation of the Passion.
4. “With my voice have I cried unto the Lord”; that is, not with the voice of the body, which is drawn out with the sound of the reverberation of the air; but with the voice of the heart, which to men speaks not, but with God sounds as a cry. By this voice Susanna was heard; and with this voice the Lord Himself commanded that prayer should be made in closets, that is, in the recesses of the heart noiselessly. Nor would one easily say that prayer is not made with this voice, if no sound of words is uttered from the body; since even when in silence we pray within the heart, if thoughts interpose alien from the mind of one praying, it cannot yet be said, “With my voice have I cried unto the Lord.” Nor is this rightly said, save when the soul alone, taking to itself nothing of the flesh, and nothing of the aims of the flesh, in prayer, speaks to God, where He only hears. But even this is called a cry by reason of the strength of its intention. “And He heard me out of His holy mountain.” We have the Lord Himself called a mountain by the Prophet, as it is written, “The stone that was cut out without hands grew to the size of a mountain.” But this cannot be taken of His Person, unless perhaps He would speak thus, out of myself, as of His holy mountain He heard me, when He dwelt in me, that is, in this very mountain. But it is more plain and unembarrassed, if we understand that God out of His justice heard. For it was just that He should raise again from the dead the Innocent who was slain, and to whom evil had been recompensed for good, and that He should render to the persecutor a meet reward, who repaid Him evil for good. For we read, “Your justice is as the mountains of God.”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)