Coming to a neighboring city, after having made a discourse, he observed a young man in the company of a fair stature and pleasing aspect, and being much taken with him, he presented him to the bishop whom he had ordained for that see, saying, "In the presence of Christ, and before this congregation, I earnestly recommend this young man to your care." The bishop took the trust upon him and promised to discharge it with fidelity. The apostle repeated his injunction and went back to Ephesus. The young man was lodged in the bishop’s house, instructed, kept to good discipline, and at length baptized and confirmed by him. When this was done, the bishop, as if the person had been now in a state of security, began to slacken the reins and be less watchful over him.
This was quickly perceived by a company of idle, debauched wretches, who allured the youth into their society. By bad company he soon forgot the precepts of the Christian religion, and passing from one degree of wickedness to another, he at length stifled all remorse, put himself at the head of a band of robbers and, taking to the highway, became the most cruel and profligate of the whole band.
Some time after, St. John was again called to the same city, and when he had settled other affairs, said to the bishop, "Restore to me the trust which Jesus Christ and I committed to you in presence of your church." The bishop was surprised, imagining he meant some trust of money. But the saint explained himself that he spoke of the young man, and the soul of his brother which he had entrusted to his care. Then the bishop, with sighs and tears, said, "Alas! he is dead."
"What did he die of?" said our saint.
The bishop replied, "He is dead to God, is turned robber, and instead of being in the church with us, he has seized on a mountain, where he lives with a company of wicked men like himself." The holy apostle having heard this, rent his garments and fetching a deep sigh said, with tears, "Oh, I what a guardian have I provided to watch over a brother’s soul" Presently he called for a horse and guide, and rode away to the mountain where the robber and his gang kept their rendezvous; and being made prisoner by their sentinels, he did not offer to fly or beg his life, but cried out, "It is for this that I am come; lead me to your captain."
They conducted the saint to him, who stood at first armed to receive him; but when he saw it was St. John, was seized with a mixture of shame and fear, and began to make off with precipitation and confusion. The apostle, forgetting his feebleness and old age, pursued him full speed, and cried out after him in these words: "Child, why have you escaped from me, your father, unarmed and an old man? My son, have compassion on me. There is room for repentance; your salvation is not irrecoverable. I will answer for you to Jesus Christ. I am ready most willingly to lay down my life for you, as Jesus Christ laid down his for all men. I will pledge my soul for yours. Stay, believe me, I am sent by Christ."
At these words the young man stood still, with his eyes fixed upon the ground; then throwing away his arms, he trembled and burst into tears. When the apostle came up, the penitent, bathed in tears, embraced his tender father, imploring forgiveness; but he hid his right hand, which had been sullied with many crimes.
The apostle, with wonderful condescension and affection, fell on his knees before him, kissed his right hand which the other endeavored in confusion to conceal, gave him fresh assurances of the divine pardon, and, earnestly praying for him, brought him back to the church. He continued some time in that place for his sake, praying and fasting with him and for him, and comforting and encouraging him with the most affecting passages of the holy scriptures. Nor did he leave the place till he had reconciled him to the church, that is, by absolution restored him to the participation of the sacraments.
(Taken from Vol. IV of “The Lives or the Fathers, Martyrs and Other Principal Saints” by the Rev. Alban Butler.)