St. Augustin on the Psalms.
50. "O remember Thy word unto Thy servant, wherein Thou hast given me hope" (ver.49). Is forgetfulness incident to God, as it is to man? Why then is it said unto Him, "O remember"? Although in other passages of holy Scripture this very word is used, as, "Why hast Thou forgotten me?"  and, "Wherefore forgettest Thou our misery?"  ...These expressions are borrowed from moral discourses on human affections; although God doth these things according to a fixed dispensation, with no failing memory, nor with an understanding obscured, nor with a will changed. When therefore it is said unto Him, "O remember," the desire of him who prayeth is displayed, because he asketh for what was promised; God is not admonished, as if the promise had escaped from His mind. "O remember," he saith, "Thy word unto Thy servant:" that is, fulfil Thy promise to Thy servant. "Wherein Thou hast given me hope:" that is, in Thy Word, since Thou hast promised, Thou hast caused me to hope.
51. "The same is my comfort in my humiliation" (ver.50). Namely, that hope which is given to the humble, as the Scripture saith: "God resisteth the proud, but giveth grace unto the humble."  Whence also our Lord Himself saith with His own lips, "For whosoever exalteth himself shall be abased; and he that humbleth himself shall be exalted."  We well understand here that humiliation also, not whereby each man humbleth himself by confessing his sins, and by not arrogating righteousness to himself; but when each man is humbled by some tribulation or mortification which his pride deserved; or when he is exercised and proved by endurance;  whence a little after this Psalm saith, "Before I was troubled, I went wrong."...And the Lord Jesus, when He foretold that this humiliation would be brought upon His disciples by their persecutors, did not leave them without a hope; but gave them one, whereby they might find comfort, in these words: "In your patience shall ye possess your souls;" and declared even of their very bodies, which might be put to death by their enemies, and seemingly be utterly annihilated, that not a hair of their heads should perish.  This hope was given to Christ's Body, that is, to the Church, that it might be a comfort to Her in her humiliation....This hope He gave in the prayer which He taught us, where He enjoined us to say, "Lead us not into temptation:"  for He in a manner implicitly promised that He would give to His disciples in their danger that which He taught them to ask for in their prayers. And indeed this Psalm is rather to be understood to speak of this hope: "For Thy word hath quickened me." Which they have rendered more closely who have put not "word," but "utterance." For the Greek has logion, which is "utterance;" not logos, which is "word."
52. The next verse is, "The proud dealt exceeding wickedly: yet have I not shrinked from Thy law" (ver.51). By the proud he wished to be understood the persecutors of the pious; and he therefore added, "yet have I not shrinked from Thy laws," because the persecution of the proud attempted to force him to do this. He saith that they dealt "exceeding wickedly," because they were not only wicked themselves, but even tried to make the godly wicked. In this humiliation, that is, in this tribulation, that hope comforted him which was given in the word of God, who promised aid, that the faith of the Martyrs might not faint; and who by the presence of His Spirit gave strength to them in their toils, that they might escape from the snare of the fowlers.  ...
53. "For I was mindful of Thy judgments from the beginning of the world, O Lord, and received comfort" (ver.52); or, as other copies have it, "and I was exhorted," that is, received exhortation. For either might be rendered for the Greek pareklhqhn. "From the beginning of the world," that is, from the birth of the human race, "I was mindful of Thy judgments" upon the vessels of wrath, which are fitted unto perdition: "and I received comfort," since through these also hast Thou shown the riches of Thy glory on the vessels of Thy mercy. 
54. "Weariness hath held me; for the ungodly that forsake Thy law" (ver.53). "Thy statutes have been my songs in the house of my pilgrimage" (ver.54). This is the low estate, in the house of mortality, of the man who sojourneth away from Paradise and the Jerusalem above, whence one going down to Jericho fell among robbers; but, in consequence of the deed of mercy which was done him by that Samaritan,  the statutes of God became his song in the house of his pilgrimage; although he was weary for the ungodly that forsook the law of God, since he was compelled to converse with them for a season in this life, until the floor be threshed. But these two verses may be adapted to the two clauses of the preceding verse, respectively.
55. "I have thought upon Thy Name, O Lord, in the night-season, and have kept Thy law" (ver.55). Night is that low estate wherein is the trouble of mortality; night is in the proud who deal exceeding wickedly; night is the fear for the ungodly who forsake the law of the Lord; night is, lastly, the house of this pilgrimage, "until the Lord come, and bring to light the hidden things of darkness, and will make manifest the counsels of the hearts, and then shall every man have praise of God."  In this night, therefore, man ought to remember the Name of the Lord; "So that he who glorieth, may glory in the Lord." 
56. Considering this, he addeth, "This was made unto me, because I sought out Thy righteousnesses" (ver.56). "Thy" righteousnesses, whereby Thou dost justify the ungodly; not mine, which never make me godly, but proud. For this man was not one of those who, "ignorant of God's righteousness, and going about to establish their own righteousness, have not submitted themselves unto the righteousness of God."  Others have better interpreted these righteousnesses, as those whereby men are justified for nought through God's grace, though by themselves they cannot be righteous, "justifications."  But what meaneth, "This was made unto me"? What is "This"? It is perhaps the law? as he had said, "and I have kept Thy law;" to which he subjoins, "This was made unto me," meaning, "This was made my law." We must therefore enquire first what was thus made unto him, next in what manner, whatever it may have been, was made unto him. "This," he saith, "was made unto me:" not "This law," for the Greek, as I have said, refuseth this sense. Perhaps then, "This night:" since the preceding sentence stands thus: "I have thought upon Thy Name, O Lord, in the night-season:" and the next words are, "This was made unto me:" since then it is not the law, it must truly be the night which is thus spoken of. What then meaneth, "I had the night-season: for I have sought out Thy righteousnesses"? Rather light had come unto him than night, since he sought out the righteousnesses of God. And it is thus rightly understood, "It was made unto me," as if it were said, It became night for my sake, that is, that it might profit me. For that low estate of mortality is not absurdly understood as night, where the hearts of mortals are hid to one another, so that from such darkness innumerable and heavy temptations arise....
 Psalm 42:9.  Psalm 44:24.  James 4:6 and 1 Pet. v. 5.  Luke 14:11 and xviii. 14.  Ecclus. ii. 4, 5.  Luke 21:17, 18.  Matthew 6:13.  Psalm 124:2.  Romans 9:22, 23.  Luke 10:30, 37.  1 Corinthians 4:5.  1 Corinthians 1:31.  Romans 10:3.  [He says: "Since the Greek hath not dikaiosunai, that is, acts of righteousness; but dikaiomata, acts of justification....For the Greek words whence these Latin words have been translated, sufficiently declare that it could not have been said of the law, for the word law is in Greek of the masculine gender, and the feminine pronoun is used in the Greek text as well."--C.]
 Psalm 44:24.
 James 4:6 and 1 Pet. v. 5.
 Luke 14:11 and xviii. 14.
 Ecclus. ii. 4, 5.
 Luke 21:17, 18.
 Matthew 6:13.
 Psalm 124:2.
 Romans 9:22, 23.
 Luke 10:30, 37.
 1 Corinthians 4:5.
 1 Corinthians 1:31.
 Romans 10:3.
 [He says: "Since the Greek hath not dikaiosunai, that is, acts of righteousness; but dikaiomata, acts of justification....For the Greek words whence these Latin words have been translated, sufficiently declare that it could not have been said of the law, for the word law is in Greek of the masculine gender, and the feminine pronoun is used in the Greek text as well."--C.]