29 But, “understand these things, you that forget God”. See how He cries, and keeps not silence, spares not. You had forgotten the Lord, did not think of your evil life. Perceive how you have forgotten the Lord. “Lest at length He seize like a lion, and there be none to deliver.” What is “like a lion”? Like a brave one, like a mighty one, like him whom none can withstand. To this he made reference when he said, “Lion.” For it is used for praise, it is used also for showing evil. The devil has been called lion: “Your adversary,” He says, “like a roaring lion, goes about seeking whom He may devour.” May it not be that whereas he has been called lion because of savage fierceness, Christ has been called Lion for wondrous mightiness? And where is that, “The Lion has prevailed of the tribe of Judah?”...
30. “Sacrifice of praise shall glorify Me”. How shall “sacrifice of praise glorify Me”? Assuredly sacrifice of praise does no wise profit evil men, because they take Your Covenant in their mouth, and do damnable things that displease Your eyes. Straightway, he says, even to them this I say, “Sacrifice of praise shall glorify Me.” For if you live ill and speakest good words, not yet do you praise: but again, if, when you begin to live well, to your merits thou dost ascribe your living well, not yet do you praise....Therefore the Publican went down justified, rather than that Pharisee. Therefore hear ye that live well, hear ye that live ill: “Sacrifice of praise shall glorify Me.” No one offers Me this sacrifice, and is evil. I say not, Let there not offer Me this any one that is evil; but no one does offer Me this, that is evil. For he that praises, is good: because if he praises, he does also live well, because if he praises, not only with tongue he praises, but life also with tongue does agree.
31. “And there is the way whereby I will show him the salvation of God.” In sacrifice of praise “is the way.” What is “the salvation of God”? Christ Jesus. And how in sacrifice of praise to us is shown Christ? Because Christ with grace came to us. These words says the Apostle: “But I live, now not I, but Christ lives in me: but that in flesh I live, in faith I live of the Son of God, who loved me, and gave Himself for me.” Acknowledge then sinners, that there would not need physician, if they were whole. For Christ died for the ungodly. When then they acknowledge their ungodlinesses, and first copy that Publican, saying, “Lord, be merciful to me a sinner:” show wounds, beseech Physician: and because they praise not themselves, but blame themselves—“So that he that glories, not in himself but in the Lord may glory,” — they acknowledge the cause of the coming of Christ, because for this end He came, that He might save sinners: for “Jesus Christ came,” he says, “into this world to save sinners; of whom I am chief.” Further, those Jews, boasting of their work, thus the same Apostle does rebuke, in saying, that they to grace belonged not, who to their merits and their works thought that reward was owing. He therefore that knows himself to belong to grace, does know what is Christ and what is Christ's because he needs grace. If grace it is called, gratis it is given; if gratis it is given, not any merits of time have preceded that it should be given....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)