St. Augustin on the Psalms.
To the end, a psalm of David himself. 
1. Christ speaks, but in the person of the Church: for what is said has reference rather to the Christian People turned unto God.
2. "Unto Thee, O Lord, have I lift up my soul" (ver.1): with spiritual longing have I lift up the soul, that was trodden down on the earth with carnal longings. "O my God, in Thee I trust, I shall not be ashamed" (ver.2). O my God, from trusting in myself I was brought even to this weakness of the flesh; and I who on abandoning God wished to be as God, fearing death from the smallest insect, was in derision ashamed for my pride; now, therefore, "in Thee I trust, I shall not be ashamed."
3. "And let not my enemies mock me." And let them not mock me, who by ensnaring me with serpent-like and secret suggestions, and prompting me with "Well done, well done," have brought me down to this. "For all that wait upon Thee shall not be confounded" (ver.3).
4. "Let them be confounded who do vain things unrighteously." Let them be confounded who act unrighteously for the acquiring things that pass away. "Make Thy ways, O Lord, known to me, and teach me Thy paths" (ver.4): not those which are broad, and lead the many to destruction;  but Thy paths, narrow, and known to few, teach Thou me.
5. "In Thy truth guide me:" avoiding error. "And teach me:" for by myself I know nothing, but falsehood. "For Thou art the God of my salvation; and for Thee have I waited all the day" (ver.5). For dismissed by Thee from Paradise, and having taken my journey into a far country,  I cannot by myself return, unless Thou meetest the wanderer: for my return hath throughout the whole tract of this world's time waited for Thy mercy.
6. "Remember Thy compassions, O Lord" (ver.6). Remember the works of Thy mercy, O Lord; for men deem of Thee as though Thou hadst forgotten. "And that Thy mercies are from eternity." And remember this, that Thy mercies are from eternity. For Thou never wast without them, who hast subjected even sinful man to vanity indeed, but in hope;  and not deprived him of so many and great consolations of Thy creation.
7. "Remember not the offences of my youth and of my ignorance" (ver.7). The offences of my presumptuous boldness and of my ignorance reserve not for vengeance, but let them be as if forgotten by Thee. "According to Thy mercy, be mindful of me, O God." Be mindful indeed of me, not according to the anger of which I am worthy, but according to Thy mercy which is worthy of Thee. "For Thy goodness, O Lord." Not for my deservings, but for Thy goodness, O Lord.
8. "Gracious and upright is the Lord" (ver.8). The Lord is gracious, since even sinners and the ungodly He so pitied, as to forgive all that is past; but the Lord is upright too, who after the mercy of vocation and pardon, which is of grace without merit, will require merits meet for the last judgment. "Wherefore He will establish a law for them that fail in the way." For He hath first bestowed mercy to bring them into the way.
9. "He will guide the meek in judgment." He will guide the meek, and will not confound in the judgment those that follow His will, and do not, in withstanding It, prefer their own. "The gentle He will teach His ways" (ver.9). He will teach His ways, not to those that desire to run before, as if they were better able to rule themselves; but to those who do not exalt the neck, nor lift the heel, when the easy yoke and the light burden is laid upon them. 
10. "All the ways of the Lord are mercy and truth" (ver.10). And what ways will He teach them, but mercy wherein He is placable, and truth wherein He is incorrupt? Whereof He hath exhibited the one in forgiving sins, the other in judging deserts. And therefore "all the ways of the Lord" are the two advents of the Son of God, the one in mercy, the other in judgment. He then attaineth unto Him holding on His ways, who seeing himself freed by no deserts of his own, lays pride aside, and henceforward bewares of the severity of His trial, having experienced the clemency of His help. "To them that seek His testament and His testimonies." For they understand the Lord as merciful at His first advent, and as the Judge at His second, who in meekness and gentleness seek His testament, when with His Own Blood He redeemed us to a new life; and in the Prophets and Evangelists, His testimonies.
11. "For Thy Name's sake, O Lord, Thou wilt be favourable to my sin; for it is manifold" (ver.11). Thou hast not only forgiven my sins, which I committed before I believed; but also to my sin, which is manifold, since even in the way there is no lack of stumbling, Thou wilt be made favourable by the sacrifice of a troubled spirit. 
12. "Who is the man that feareth the Lord?" from which fear he begins to come to wisdom. "He shall establish a law for him in the way, which he hath chosen" (ver.12). He shall establish a law for him in the way, which in his freedom he has taken, that he may not sin now with impunity.
13. "His soul shall dwell in good, and his seed shall, by inheritance, possess the earth" (ver.13). And his work shall possess the stable inheritance of a renewed body.
14. "The Lord is the stay of them that fear Him" (ver.14). Fear seems to belong to the weak, but the Lord is the stay of them that fear Him. And the Name of the Lord, which hath been glorified throughout the whole world, is a stay to them that fear Him. "And His testament, that it may be manifested unto them." And He maketh His testament to be manifested unto them, for the Gentiles and the bounds of the earth are Christ's inheritance.
15. "Mine eyes are ever unto the Lord; for He shall pluck my feet out of the snare" (ver.15). Nor would I fear the dangers of earth, while I look not upon the earth: for He upon whom I look, will pluck my feet out of the snare.
16. "Look upon me, and have mercy upon me; for I am single and poor" (ver.16). For I am a single people, keeping the lowliness of Thy single Church, which no schisms or heresies possess.
17. "The tribulations of my heart have been multiplied" (ver.17). The tribulations of my heart have been multiplied by the abounding of iniquity and the waxing cold of love.  "O bring Thou me out of my necessities." Since I must needs bear this, that by enduring unto the end I may be saved, bring Thou me out of my necessities.
18. "See my humility and my travail" (ver.18). See my humility, whereby I never, in the boast of righteousness, break off from unity; and my travail, wherein I bear with the unruly ones that are mingled with me. "And forgive all my sins." And, propitiated by these sacrifices, forgive all my sins, not those only of youth and my ignorance before I believed, but those also which, living now by faith, I commit through infirmity, or the darkness of this life.
19. "Consider mine enemies, how they are multiplied" (ver.19). For not only without, but even within, in the Church's very communion, they are not wanting. "And with an unrighteous hate they hate me." And they hate me who love them.
20. "Keep my soul, and deliver me." Keep my soul, that I turn not aside to imitate them; and draw me out from the confusion wherein they are mingled with me. "Let me not be confounded, for I have put my trust in Thee" (ver.20). Let me not be confounded, if haply they rise up against me: for not in myself, but in Thee have I put my trust.
21. "The innocent and the upright have cleaved to me, for I have waited for Thee, O Lord" (ver.21). The innocent and the upright, not in bodily presence only, as the evil, are mingled with me, but in the agreement of the heart in the same innocence and uprightness cleave to me: for I have not fallen away to imitate the evil; but I have waited for Thee, expecting the winnowing of Thy last harvest. 
22. "Redeem Israel, O God, out of all his troubles" (ver.22). "Redeem Thy people, O God," whom Thou hast prepared to see Thee, out of his troubles, not those only which he bears without, but those also which he bears within.
 Lat. XXIV.  [Alphabetical Psalm.--C.]  Matthew 7:13.  Luke 15:13.  Romans 8:20.  Matthew 11:30.  [Here our author, as did St. Chrysostom, treats true contrition as completed by pardon, without sacramental absolution.--C.]  Matthew 24:12.  [So the dying Jacob, Genesis 49:18.--C.]
 [Alphabetical Psalm.--C.]
 Matthew 7:13.
 Luke 15:13.
 Romans 8:20.
 Matthew 11:30.
 [Here our author, as did St. Chrysostom, treats true contrition as completed by pardon, without sacramental absolution.--C.]
 Matthew 24:12.
 [So the dying Jacob, Genesis 49:18.--C.]