This is a must-not-miss as far too many do not know of this story of Saint John in his elder years–KSH.
Listen to a tale, which is not a mere tale, but a narrative concerning John the apostle, which has been handed down and treasured up in memory. For when, after the tyrant’s death, he returned from the isle of Patmos to Ephesus, he went away upon their invitation to the neighboring territories of the Gentiles, to appoint bishops in some places, in other places to set in order whole churches, elsewhere to choose to the ministry some one of those that were pointed out by the Spirit.
7. When he had come to one of the cities not far away (the name of which is given by some ), and had consoled the brethren in other matters, he finally turned to the bishop that had been appointed, and seeing a youth of powerful physique, of pleasing appearance, and of ardent temperament, he said, ‘This one I commit to you in all earnestness in the presence of the Church and with Christ as witness.’ And when the bishop had accepted the charge and had promised all, he repeated the same injunction with an appeal to the same witnesses, and then departed for Ephesus.
8. But the presbyter taking home the youth committed to him, reared, kept, cherished, and finally baptized him. After this he relaxed his stricter care and watchfulness, with the idea that in putting upon him the seal of the Lord he had given him a perfect protection.
9. But some youths of his own age, idle and dissolute, and accustomed to evil practices, corrupted him when he was thus prematurely freed from restraint. At first they enticed him by costly entertainments; then, when they went forth at night for robbery, they took him with them, and finally they demanded that he should unite with them in some greater crime.
10. He gradually became accustomed to such practices, and on account of the positiveness of his character, leaving the right path, and taking the bit in his teeth like a hard-mouthed and powerful horse, he rushed the more violently down into the depths.
11. And finally despairing of salvation in God, he no longer meditated what was insignificant, but having committed some great crime, since he was now lost once for all, he expected to suffer a like fate with the rest. Taking them, therefore, and forming a band of robbers, he became a bold bandit-chief, the most violent, most bloody, most cruel of them all.
12. Time passed, and some necessity having arisen, they sent for John. But he, when he had set in order the other matters on account of which he had come, said, ‘Come, O bishop, restore us the deposit which both I and Christ committed to you, the church, over which you preside, being witness.’
13. But the bishop was at first confounded, thinking that he was falsely charged in regard to money which he had not received, and he could neither believe the accusation respecting what he had not, nor could he disbelieve John. But when he said, ‘I demand the young man and the soul of the brother,’ the old man, groaning deeply and at the same time bursting into tears, said, ‘He is dead.’ ‘How and what kind of death?’ ‘He is dead to God,’ he said; ‘for he turned wicked and abandoned, and at last a robber. And now, instead of the church, he haunts the mountain with a band like himself.’
14. But the Apostle rent his clothes, and beating his head with great lamentation, he said, ‘A fine guard I left for a brother’s soul! But let a horse be brought me, and let some one show me the way.’ He rode away from the church just as he was, and coming to the place, he was taken prisoner by the robbers’ outpost.
15. He, however, neither fled nor made entreaty, but cried out, ‘For this did I come; lead me to your captain.’
16. The latter, meanwhile, was waiting, armed as he was. But when he recognized John approaching, he turned in shame to flee.
17. But John, forgetting his age, pursued him with all his might, crying out, ‘Why, my son, do you flee from me, your own father, unarmed, aged? Pity me, my son; fear not; you have still hope of life. I will give account to Christ for you. If need be, I will willingly endure your death as the Lord suffered death for us. For you will I give up my life. Stand, believe; Christ has sent me.’
18. And he, when he heard, first stopped and looked down; then he threw away his arms, and then trembled and wept bitterly. And when the old man approached, he embraced him, making confession with lamentations as he was able, baptizing himself a second time with tears, and concealing only his right hand.
19. But John, pledging himself, and assuring him on oath that he would find forgiveness with the Saviour, besought him, fell upon his knees, kissed his right hand itself as if now purified by repentance, and led him back to the church. And making intercession for him with copious prayers, and struggling together with him in continual fastings, and subduing his mind by various utterances, he did not depart, as they say, until he had restored him to the church, furnishing a great example of true repentance and a great proof of regeneration, a trophy of a visible resurrection.
(From Eusebius which may be found there [III.23]).