1 Now the story which gave occasion to this prophecy may be easily recognised in the second book of Kings. For there Chusi, the friend of king David, went over to the side of Abessalon, his son, who was carrying on war against his father, for the purpose of discovering and reporting the designs which he was taking against his father, at the instigation of Achitophel, who had revolted from David's friendship, and was instructing by his counsel, to the best of his power, the son against the father. But since it is not the story itself which is to be the subject of consideration in this Psalm, from which the prophet has taken a veil of mysteries, if we have passed over to Christ, let the veil be taken away. And first let us inquire into the signification of the very names, what it means. For there have not been wanting interpreters, who investigating these same words, not carnally according to the letter, but spiritually, declare to us that Chusi should be interpreted silence; and Gemini, right-handed; Achitophel, brother's ruin. Among which interpretations, Judas, that traitor, again meets us, that Abessalon should bear his image, according to that interpretation of it as a father's peace; in that his father was full of thoughts of peace toward him: although he in his guile had war in his heart, as was treated of in the third Psalm. Now as we find in the Gospels that the disciples of our Lord Jesus Christ are called sons, so in the same Gospels we find they are called brethren also. For the Lord on the resurrection says, “Go and say to My brethren.” And the Apostle calls Him “the first begotten among many brethren.” The ruin then of that disciple, who betrayed Him, is rightly understood to be a brother's ruin, which we said is the interpretation of Achitophel. Now as to Chusi, from the interpretation of silence, it is rightly understood that our Lord contended against that guile in silence, that is, in that most deep secret, whereby “blindness happened in part to Israel,” when they were persecuting the Lord, that the fullness of the Gentiles might enter in, and “so all Israel might be saved.” When the Apostle came to this profound secret and deep silence, he exclaimed, as if struck with a kind of awe of its very depth, “O the depth of the riches of the wisdom and knowledge of God! How unsearchable are His judgments, and His ways past finding out! For who has known the wind of the Lord, or who has been His counsellor?” Thus that great silence he does not so much discover by explanation, as he sets forth its greatness in admiration. In this silence the Lord, hiding the sacrament of His adorable passion, turns the brother's voluntary ruin, that is, His betrayer's impious wickedness, into the order of His mercy and providence: that what he with perverse mind wrought for one Man's destruction, He might by providential overruling dispose for all men's salvation. The perfect soul then, which is already worthy to know the secret of God, sings a Psalm unto the Lord, she sings “for the words of Chusi,” because she has attained to know the words of that silence: for among unbelievers and persecutors there is that silence and secret. But among His own, to whom it is said, Now I call you no more servants; for the servant knows not what his lord does; but I have called you friends, for all things that I have heard of My Father I have made known unto you: among His friends, I say, there is not the silence, but the words of the silence, that is, the meaning of that silence set forth and manifested. Which silence, that is, Chusi, is called the son of Gemini, that is, righthanded. For what was done for the Saints was not to be hidden from them. And yet He says, “Let not the left hand know what the right hand does.” The perfect soul then, to which that secret has been made known, sings in prophecy “for the words of Chusi,” that is, for the knowledge of that same secret. Which secret God at her right hand, that is, favourable and propitious unto her, has wrought. Wherefore this silence is called the Son of the right hand, which is, “Chusi, the son of Gemini.”
2. “O Lord my God, in You have I hoped: save me from all them that persecute me, and deliver me”. As one to whom, already perfected, all the war and enmity of vice being overcome, there remains no enemy but the envious devil, he says, “Save me from all them that persecute me, and deliver me: lest at any time he tear my soul as a lion.” The Apostle says, “Your adversary the devil, as a roaring lion, walks about, seeking whom he may devour.” Therefore when the Psalmist said in the plural number, “Save me from all them that persecute me:” he afterwards introduced the singular, saying, “lest at any time he tear my soul as a lion.” For he does not say, lest at any time they tear: he knew what enemy and violent adversary of the perfect soul remained. “Whilst there be none to redeem, nor to save:” that is, lest he tear me, while Thou redeemest not, nor savest. For, if God redeem not, nor save, he tears.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)