4 He proceeds accordingly to say, “Pity me, O Lord, for I am weak: heal me, O Lord, for my bones are troubled”, that is, the support of my soul, or strength: for this is the meaning of “bones.” The soul therefore says, that her strength is troubled, when she speaks of bones. For it is not to be supposed, that the soul has bones, such as we see in the body. Wherefore, what follows tends to explain it, “and my soul is troubled exceedingly”, lest because he mentioned bones, they should be understood as of the body. “And You, O Lord, how long?” Who does not see represented here a soul struggling with her diseases; but long kept back by the physician, that she may be convinced what evils she has plunged herself into through sin? For what is easily healed, is not much avoided: but from the difficulty of the healing, there will be the more careful keeping of recovered health. God then, to whom it is said, “And You, O Lord, how long?” must not be deemed as if cruel: but as a kind convincer of the soul, what evil she has procured for herself. For this soul does not yet pray so perfectly, as that it can be said to her, “Whilst you are yet speaking I will say, Behold, here I am.” That she may at the same time also come to know, if they who do turn meet with so great difficulty, how great punishment is prepared for the ungodly, who will not turn to God: as it is written in another place, “If the righteous scarcely be saved, where shall the sinner and ungodly appear?”
5. “Turn, O Lord, and deliver my soul”. Turning herself she prays that God too would turn to her: as it is said, “Turn ye unto Me, and I will turn unto you, says the Lord.” Or is it to be understood according to that way of speaking, “Turn, O Lord,” that is make me turn, since the soul in this her turning feels difficulty and toil? For our perfected turning finds God ready, as says the Prophet, “We shall find Him ready as the dawn.” Since it was not His absence who is everywhere present, but our turning away that made us lose Him; “He was in this world,” it is said, “and the world was made by Him, and the world knew Him not.” If, then, He was in this world, and the world knew Him not, our impurity does not endure the sight of Him. But while we are turning ourselves, that is, by changing our old life are fashioning our spirit; we feel it hard and toilsome to be wrested back from the darkness of earthly lusts, to the serene and quiet and tranquillity of the divine light. And in such difficulty we say, “Turn, O Lord,” that is, help us, that that turning may be perfected in us, which finds You ready, and offering Yourself for the fruition of them that love You. And hence after he said, “Turn, O Lord,” he added, “and deliver my soul:” cleaving as it were to the entanglements of this world, and suffering, in the very act of turning, from the thorns, as it were, of rending and tearing desires. “Make me whole,” he says, “for Your pity's sake.” He knows that it is not of his own merits that he is healed: for to him sinning, and transgressing a given command, was just condemnation due. Heal me therefore, he says, not for my merit's sake, but for Your pity's sake.
6. “For in death there is no one that is mindful of You”. He knows too that now is the time for turning unto God: for when this life shall have passed away, there remains but a retribution of our deserts. “But in hell who shall confess to You?” That rich man, of whom the Lord speaks, who saw Lazarus in rest, but bewailed himself in torments, confessed in hell, yea so as to wish even to have his brethren warned, that they might keep themselves from sin, because of the punishment which is not believed to be in hell. Although therefore to no purpose, yet he confessed that those torments had deservedly lighted upon him; since he even wished his brethren to be instructed, lest they should fall into the same. What then is, “But in hell who will confess to You?” Is hell to be understood as that place, whither the ungodly will be cast down after the judgment, when by reason of that deeper darkness they will no more see any light of God, to whom they may confess anything? For as yet that rich man by raising his eyes, although a vast gulf lay between, could still see Lazarus established in rest: by comparing himself with whom, he was driven to a confession of his own deserts. It may be understood also, as if the Psalmist calls sin, that is committed in contempt of God's law, death: so as that we should give the name of death to the sting of death, because it procures death. “For the sting of death is sin.” In which death this is to be unmindful of God, to despise His law and commandments: so that by hell the Psalmist would mean that blindness of soul which overtakes and enwraps the sinner, that is, the dying. “As they did not think good,” the Apostle says, “to retain God in” their “knowledge, God gave them over to a reprobate mind.” From this death, and this hell, the soul earnestly prays that she may be kept safe, while she strives to turn to God, and feels her difficulties.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)