17 The Psalm then continues: “His delight was in cursing, and it shall happen to him”. Although Judas loved cursing, both in stealing from the money bag, and selling and betraying the Lord: nevertheless, that people more openly loved cursing, when they said, “His blood be on us, and on our children.” “He loved not blessing, therefore it shall be far from him.” Such was Judas indeed, since he loved not Christ, in whom is everlasting blessing; but the Jewish people still more decidedly refused blessing, unto whom he who had been enlightened by the Lord said, “Will ye also be His disciples?” “He clothed himself with cursing, like as with a raiment:” either Judas, or that people. “And it came into his bowels like water.” Both without, then, and within; without, like a garment; within, like water: since he has come before the judgment-seat of Him “who has power to destroy both body and soul in hell;” the body without, the soul within. “And like oil into his bones.” He shows that he works evil with delight, and stores up cursing for himself, that is, everlasting punishment; for blessing is eternal life. For at present evil deeds are his delight, flowing like water into his bowels, like oil into his bones; but it is styled cursing, because God has appointed torments for such men.
18. “Let it be unto him as the cloak which covers him”. Since he has before spoken of the cloak, why does he repeat it? When he said, “He clothed himself with cursing as with a raiment;” does the raiment with which he is “covered” differ from that with which he is “clothed”? For every man is clothed with his tunic, covered with his cloak; and what is this, save boasting in iniquity, even in the sight of men? “and as the girdle,” he says, “that he is always girded withal.” Men are girded chiefly that they may be better fit for toil, that they may not be hindered by the folds of their dress. He therefore girds himself with curses, who designs an evil which he has carefully contrived, not on a sudden impulse, and who learns in such a manner to do evil, that he is always ready to commit it.
19. “This is the work of them that slander me before the Lord”. He said not, “their reward,” but, “their work:” for it is clear that by the clothing, covering, water, oil, and girdle, he was describing the very works by which eternal curses are procured. It is not then one Judas, but many, of whom it is said, “This is the work of them that slander me before the Lord.” Although indeed the plural number might have been put for the singular; even as, when Herod died, it was said by the Angel, “They are dead which sought the young Child's life.” But who slander Christ more before the Lord, than they who slander the very words of the Lord, by declaring that it is not He whom the Law of the Lord and His Prophets announced beforehand? “And of those that speak evil against my soul:” by denying that He, when He had willed, could have arisen: though He says, “I have power to lay down My life, and I have power to take it again.”
20. “But work Thou with me, O Lord God”. Some have thought “mercifully” should be understood, some have actually added it; but the best copies have the words thus: “But work Thou with me, O Lord God, for Your Name's sake.” Whence a higher sense should not be passed over, supposing the Son to have thus addressed the Father, “Deal Thou with Me,” since the works of the Father and of the Son are the same. Where although we understand mercy—for these words follow, “for sweet is Your mercy,”— because he said not, “In me,” or, “over me;” or anything of this sort: but, “work Thou with Me;” we rightly understand that the Father and Son together work mercifully towards the vessels of mercy. “Work with me,” may also be understood to mean, help me. We use this expression in our daily language, when we are speaking of anything which is in our favour; “It works with us.” For the Father aids the Son, as far as the Deity aids Man, on account of His having assumed the “form of a servant,” to which Man, God, and to which “Form of a servant,” the Lord too is Father. For in the “form of God,” the Son needs not aid, for He is equally all-powerful with the Father, on which account He also is the helper of men....And because when he had said, “Work Thou with me,” he added, “for Your Name's sake,” he has commended grace. For without previous deserving works, human nature was raised to such a height, that the whole in one, the Word and Flesh, that is, God and Man, was styled the Only-begotten Son of God. And this was done that that which had been lost might be sought by Him who had created it, through that which had not been lost; whence the following words, “For Your mercy is sweet.”
21. “O deliver me, for I am needy and poor”. Need and poverty is that weakness, through which He was crucified. “And my heart is disturbed within me.” This alludes to those words which He spoke when His Passion was drawing near, “My soul is exceeding sorrowful, even unto death.”
22. “I go hence like a shadow that declines”. By this he signified death itself. For as night comes of the shadow's declining, so death comes of mortal flesh. “And am driven away as the locusts.” This I think would be more suitably understood of His members, that is, of His faithful disciples. That he might make it much plainer, he preferred writing “locusts” in the plural number: although many may be understood where the singular number is used, as in that passage, “He spoke, and the locust came;” but it would have been more obscure. His disciples, then, were driven away, that is, were put to flight by persecutors, either the multitude of whom He wished to be signified by the word locusts, or their passing from one place to another.
23. “My knees are weak through fasting”. We read, that our Lord Christ underwent a fast of forty days: but had fasting so great power over Him, that His knees were weakened? Or is this more suitably understood of His members, that is, of His saints? “And my flesh is changed because of the oil;” because of spiritual grace. Whence Christ was so called from the Greek word, chrisma, which signifies unction. But the flesh was changed through the oil, not for the worse, but for the better, that is, rising from the dishonour of death to the glory of immortality....His flesh was not yet changed. But whether the Holy Spirit be represented by water through the notion of ablution or irrigation, or by oil through that of exultation and the inflaming of charity; It does not differ from Itself, because Its types are different. For there is a great difference between the lion and the lamb, and yet Christ is represented by both....
24. “I became also a reproach unto them”: through the death of the Cross. “For Christ has redeemed us from the curse of the law, being made a curse for us.” “They looked upon Me, and shaked their heads.” Because they beheld His crucifixion, without beholding His resurrection: they saw when His knees were weakened, they saw not when His flesh was changed.
25. “Help me, O Lord my God: O save me according to Your mercy”. This may be referred to the whole, both to the Head and to the body: to the Head, owing to His having taken the form of a servant; to the body, on account of the servants themselves. For He might even in them have said unto God, “Help Me:” and, “O save Me:” as in them He said unto Paul, “Why do you persecute Me”? The following words, “according to Your mercy,” describe grace given gratuitously, not according to the merit of works.
26. “And let them know how that this is Your Hand, and that Thou, Lord, hast made it”. He said, “Let them know,” of those for whom He even prayed while they were raging; for even those who afterwards believed in Him were among the crowd who shook their heads in mockery of Him. But let those who ascribe unto God the shape of the human body, learn in what sense God has a hand. Let us therefore understand, that the Hand of God means Christ: whence it is elsewhere said, “Unto whom is the arm of the Lord revealed?”...
Source: The Enarrations, or Expositions, on the Psalms (New Advent)