5 But when your heart has not been turned aside, O member of Christ, when your heart has not been turned aside “to wicked words, to making excuses in sins, with men that work in iniquity,” you shall also not unite with their elect. For this follows, “And I will not unite with their elect.” Who are “their elect”? Those who justify themselves. Who are their elect? Those “who trust in themselves that they are righteous, and despise others,” as the Pharisee said in the temple, “Lord, I thank You that I am not as other men are.” Who are their elect? “This Man, if He were a prophet, would know what manner of woman this is that touched His feet.” Here you recognise the words of that other Pharisee, who invited our Lord to his house; when the woman of that city, who was a sinner, came and approached His Feet....
For even this woman herself, “if her heart had turned aside to wicked words,” would not have lacked wherewith to defend her sins. Do not women daily, her equals in defilement, but not her equals in confession, harlots, adulteresses, doers of shameful deeds, defend their sins? If they have not been seen, they deny them: if they have been caught and convicted, or have done their deeds openly, they defend them. And how easy is their defence, how ready, yet how headlong; how common, yet how blasphemous! “Had God not willed it, I had not done it: God willed it: fortune willed it: fate willed it.”...These are the defences of “the elect” of this world. But let the members of Christ, the Body of Christ, say, let Christ say in the name of His Body, “Turn not Thou aside, My Heart, to wicked words,” etc., “and I will not unite with their elect.”...
6. “With men that work wickedness.” What wickedness? Let me mention some sinful wickedness of theirs. Let me tell you one open sinful wickedness, which they acknowledge. They say, it is better for a man to be an usurer than a husbandman. Thou ask the reason, and they assign one....He vexes the members of Christ, who cleanses the earth with a furrow: he vexes the members of Christ, who pulls grass from the earth: he vexes the members of Christ, who plucks an apple from a tree. To avoid committing their imaginary murders in the farm, he commits real murders in usury. He deals no bread to the needy. See whether there can be greater unrighteousness than this righteousness. He deals not bread to the hungry. You ask, why? Lest the beggar receive the life which is in the bread, which they call a member of God, the substance of God, and bind it in flesh. What then are you doing? Why do you eat? Have you not flesh? Yes; but we, they say, forasmuch as we are enlightened by faith in Manes, by our prayers and our Psalms, forasmuch as we are elect, we cleanse thereby that bread, and transmit it into the treasure-house of the heavens. Such are the elect, that they are not to be saved by God, but saviours of God. And this is Christ, they say, crucified in the whole universe. I received in the Gospel Christ a Saviour, but you are in your books the saviours of Christ. Plainly you are blasphemers of Christ, and therefore not to be saved by Christ. Therefore lest a crumb be given to the hungry, and in the crumb a member of Christ suffer, is the hungry to die of hunger? False mercy to a crumb causes true murder of a man. But who are their elect? “Turn not thou aside, my heart, to wicked words, and I will not unite with their elect.”
7. “The righteous One shall amend me in mercy, and convict me”. Behold the sinner confessing. He desires to be amended in mercy, rather than praised deceitfully....“Shall convict me,” but “in mercy:” shall convict, yet hates not: yea, shall all the more convict, because He hates not. And why does he therefore give thanks? Because, “rebuke a wise man, and he will love you.” “The righteous One shall amend me.” Because He persecutes you? God forbid. He requires rather amending himself, who amends in hate. Wherefore then does He amend? “In mercy. And shall convict me.” Wherein? “In mercy. For the oil of a sinner shall not enrich my head.” My head shall not grow by flattery. Undue praise is flattery: undue praise of a flatterer is “the oil of a sinner.” Therefore men too, when they have mocked any one with false praise, say, “I have anointed his head.” Love then to be “convicted by the righteous One in mercy;” love not to be praised by a sinner in mockery. Have oil in yourselves, and you shall not seek the “oil of a sinner.”...
Source: The Enarrations, or Expositions, on the Psalms (New Advent)