Lamed
89 The man who speaks in this Psalm, as if he were tired of human mutability, whence this life is full of temptations, among his tribulations, on account of which he had above said, “The wicked have persecuted me;” and, “They have almost made an end of me upon earth”; burning with longings for the heavenly Jerusalem; looked up to the realms above, and said, “O Lord, Your word endures for ever in heaven;” that is, among Your Angels who serve everlastingly in Your armies, without desertion.
90. But the next verse, after heaven, pertains consequently to earth. For this is one verse of the eight which relate to this letter. For eight verses are appended to each of these Hebrew letters, until this long Psalm be ended. “Your truth also remains from one generation to the other: You have laid the foundation of the earth, and it abides”. Beholding therefore the earth next after heaven with the gaze of a faithful mind, he finds in it generations which are not in heaven, and says, “Your truth remains from one generation to the other:” signifying all generations by this expression, from which the Truth of God was never absent in His saints, at one time fewer, at one time more in number, according as the times happened or shall happen to vary; or wishing two particular generations to be understood, one pertaining to the Law and the Prophets, another to the Gospel....
91. “Day continues according to Your ordinance”. For all these things are day: “and this is the day which the Lord has made: let us rejoice and be glad in it:” and “let us walk honestly as in the day.” “For all things serve You.” He said all things of some: “all” which belong to this day “serve You.” For the ungodly of whom it is said, “I have compared your mother unto the night,” do not serve You.
92. He then looks back towards the source of this earth's deliverance, which caused it to abide when founded; and adds, “If my delight had not been in Your law, I should perchance have perished in my humiliation”. This is the law of faith, not a vain faith, but that which works through love. Through this grace is gained, which makes men courageous in temporal tribulation, that they may not perish in the humiliation of mortality.
93. “I will never forget,” he says, “Your righteousnesses, for with them You have quickened me”. Behold how it was that he did not perish in his humiliation. For, save God quickens, what is man, Who can indeed kill, but cannot quicken himself?
94. He next adds: “I am Yours: O save me, for I have sought Your righteousnesses”. We must not understand lightly the words, “I am Yours.” For what is not His? Why then is it that the Psalmist has commended himself unto God somewhat in a more familiar sense, in these words, “I am Yours: O save me;” save because he wished it to be understood that he had desired to be his own only to his harm, which is the first and the greatest evil of disobedience? And as if he should say, I wished to be my own, and I lost myself: “I am Yours,” he says, “O save me, for I have sought Your righteousnesses;” not my own inclinations, whereby I was my own, but “Your righteousnesses,” that I might now be Yours.
95. “The ungodly,” he says, “have awaited me that they might destroy me; but I have understood Your testimonies”. What means, “that they might destroy me”? Did he then fear that he should perish altogether at the death of his body? God forbid! And what means, “have awaited me,” save that he should consent with them unto iniquity? For then they would destroy him. And he has said why he has not perished: “I understood Your testimonies.” The Greek word, Μαρτύρια, sounds more familiarly to the ears of the Church. For though they should slay me not consenting unto them, yet while I confessed Your testimonies (martyria) I should not perish; but they who, that they might destroy me, were waiting till I should consent unto them, tortured me even when I did confess them. Yet he did not leave that which he had understood, looking on it and seeing an end without end, if only he should persevere unto the end.
96. Lastly, he next says, “I have seen an end of all consummation: but Your commandment is exceeding broad”. For he had entered into the sanctuary of God, and had understood the end. Now “all consummation” appears to me in this place to signify, the striving even unto death for the truth, and the endurance of every evil for the true and chief good: the end of which consummation is to excel in the kingdom of Christ, which has no end; and there to have without death, without pain, and with great honour, life, acquired by the death of this life, and by sorrows and reproaches. But in what he has added, “Your commandment is exceeding broad;” I understand only love. For what would it have profited him, whatever death impended over him, in the midst of whatsoever torment, to confess those testimonies, if love were not in the confessor?...Broad therefore is the commandment of charity, that twofold commandment, whereby we are enjoined to love God and our neighbour. But what is broader than that, “on” which “hang all the Law and the Prophets”?
Source: The Enarrations, or Expositions, on the Psalms (New Advent)