13 “O God, my life I have told out to You”. For that I live has been Your doing, and for this reason I tell out my life to You. But did not God know that which He had given? What is that which you tell out to Him? Will you teach God? Far be it. Therefore why says he, “I have told out to You”? Is it perchance because it profits You that I have told out my life? And what does it profit God? To the advantage of God it does profit. I have told out to God my life, because that life has been God's doing.
In like manner as his life Paul the Apostle did tell out, saying, “I that before was a blasphemer and a persecutor and injurious,” he shall tell out his life. “But mercy I have obtained.” He has told out his life, not for himself, but for Him: because he has told it out in such sort, that in Him men believe, not for his own advantages, but for the advantages of Him....“O God, my life I have told out to You. You have put my tears in Your sight.” You have hearkened to me imploring You. “As also in Your promise.” Because as You had promised this thing, so You have done. You have said You would hearken to one weeping. I have believed, I have wept, I have been hearkened unto; I have found You merciful in promising, true in repaying.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)