Now I will relate how You set me free from a craving for sexual gratification which fettered me like a tight-drawn chain, and from my enslavement to worldly affairs: I will confess to Your name, O Lord, my helper and my redeemer.
While he had been sitting under the Gospel preaching of Ambrose of Milan, Augustine of Hippo had the occasion to hear of the testimonies of the rhetorician Victorinus and of Anthony and the Egyptian monks—schooled philosophers whom Augustine held in high esteem, men who had come under the conviction of the Holy Spirit by the Scriptures and were humbled to repentance and faith in Jesus Christ. At this point he could bear the convictions of his own soul no longer. He confronted his dear friend Alypius and spoke of the inner turmoil he was experiencing.
Within the house of my spirit the violent conflict raged on, the quarrel with my soul that I had so powerfully provoked in our secret dwelling, my heart, and at the height of it I rushed to Alypius with my mental anguish plain upon my face. “What is happening to us?” I exclaimed. “What does this mean? What did you make of it? The untaught are rising up and taking heaven by storm, while we with all our dreary teachings are still groveling in this world of flesh and blood!”
“Adjacent to our lodgings was a small garden. … The tumult in my breast had swept me away to this place, where no one would interfere with the blazing dispute I had engaged in with myself until it should be resolved. … All I knew was that I was going mad, but for the sake of my sanity, and dying that I might live.
Augustine records the next moments as a battle between the pleasures of his soul. What had thus far halted his conversion was the pleasure of sin competing with the pleasures of knowing and enjoying God in Christ.
The frivolity of frivolous aims, the futility of futile pursuits, these things that had been my cronies of long standing, still held me back, plucking softly at my garment of flesh and murmuring in my ear, “Do you mean to get rid of us? Shall we never be your companions again after that moment…never…never again? From that time onward so-and-so will be forbidden to you, all your life long.” … “Do you imagine you will be able to live without these things?”
At this point, Piper comments, “But he began to see more clearly that the gain was far greater than the loss, and by a miracle of grace he began to see the beauty of chastity in the presence of Christ.”
The taunts had begun to sound much less persuasive, however; for a revelation was coming to me from that country toward which I was facing, but into which I trembled to cross. There I beheld the chaste, dignified figure of continence. Calm and cheerful was her manner, though modest, pure and honorable her charm as she coaxed me to come and hesitate no longer, stretching kindly hands to welcome and embrace me.
And that was the last straw:
I flung myself down somehow under a fig tree and gave free rein to the tears that burst from eyes like rivers… I uttered cries of misery: “Why must I go on saying, ‘Tomorrow…tomorrow’? Why not now? Why not put an end to my depravity this very hour?” Suddenly I heard a voice from a house nearby—perhaps a voice of some boy or girl, I do not know—singing over and over again, “Pick it up and read, pick it up and read.” My expression immediately altered and I began to think hard whether children ordinarily repeated a ditty like this in any sort of game, but I could not recall ever having heard it anywhere else. I stemmed the flood of tears and rose to my feet, believing that this could be nothing other than a divine command to open the Book and read the first passage I chanced upon. …
“Strung into action, I returned to the place where Alypius was sitting, for on leaving it I had put down there the book of the apostle’s letters. I snatched it up, opened it and read in silence the passage on which my eyes first lighted: “Not in dissipation and drunkenness, nor in debauchery and lewdness, nor in arguing and jealousy; but put on the Lord Jesus Christ, and make no provision for the flesh or the gratification of your desires.” I had no wish to read further, nor was there need. No sooner had I reached the end of that verse than the light of certainty flooded my heart and all dark shades of doubt fled away.
In that moment, God had shone in Augustine’s heart to give the Light of the knowledge of the glory of God in the face of Christ (2 Corinthians 4:6).
The great Princeton theologian B. B. Warfield wrote of Augustine’s conversion: “Thus a soul was brought to its God, and made so firmly His that throughout a long life of service to Him it never knew the slightest wavering of its allegiance.” Historian Stephen Nichols cleverly quips, “In the garden paradise was lost, and in a garden it was, for Augustine, regained.”
But perhaps the best words to describe Augustine’s conversion are his own:
How sweet all at once it was for me to be rid of those fruitless joys which I had once feared to lose! … You drove them from me, you who are the true, sovereign joy. You drove them from me and took their place, you who are sweeter than all pleasure, though not to flesh and blood, you who outshine all light, yet are hidden deeper than any secret in our hearts, you who surpass all honor, though not in the eyes of men who see all honor in themselves. … O Lord my God, my Light, my Wealth, and my Salvation. 
May the Lord God Himself drive from His people the fruitless joys which we foolishly fear to lose. And may He do so, not by extinguishing our pleasure, but by directing us to the Source of all pleasure: to Himself — the true, Sovereign Joy.
 Confessions, VIII.6.13.
 Confessions, VIII.8.19.
 Confessions, VIII.26.
 Piper, The Legacy of Sovereign Joy, 52.
 Confessions, VIII.26.
 Confessions, VIII.12.28-29.
 Warfield, Calvin and Augustine, 363.
 Nichols, Pages from Church History, 76.
 Confessions, IX.1.