In mystical theology we were taught that there were three steps towards the perfection of Charity. Charity is, of course, Christian Perfection. These three steps could be allegorically compared to the three Divine Calls underwent by the apostles.
The first Divine Call is when Christ called Peter and Andrew, the brothers James and John. At this first Divine Call they underwent their first conversion. They were already following John the Baptist and so they were prepared for the first call of Christ. The results were dramatic; Peter and Andrew left the boats and nets and the Zebedees left their boats and father. Matthew left his toll booth. They became fishers of man.
They left all things and made provision that there was no way by which they could go back to those things. When Christ preached to the crowd who left Him, Christ asked His apostles: “Will you also leave me?” And they answered “Lord, Where shall we go?” That is how they left all things. They had no place to go if they left Christ. Now that is a true following of Christ. Many followed Christ. But those who left all things and followed Christ became the true disciples. Those who followed Christ without leaving all things went back to all those things.
The young rich man who wanted to follow Christ was told to go home, sell all his things and give it to the poor and then follow Christ. Because he could not part with his possessions, he had something to come back to and, thereby, was unable to follow Christ. He failed Christ’s first Divine Call and as a consequence could not undergo his First Conversion.
The result of the First Divine Call that signaled the first Conversion of the apostles is a knowledge of the beauty and godliness of the teachings of Christ. This is what made them attached to Christ and not the fact that they had nothing to go back to.
The second conversion of St. Peter was during the Passion. He denied Christ three times and Christ looked at him. The look of Christ was Christ’s Second call that initiated the Second conversion of St. Peter. Christ’s look was an invitation to Peter to completely depend in humility on God’s grace since left to himself he would end up betraying Christ. Peter’s conversion consisted in realizing his need for complete dependency on the grace of God. John the Evangelist, too, who ran away briefly was called and underwent his Second conversion under the cross.
The result of their second conversion is knowledge and understanding of the Passion of Christ. So Peter who, before, did not want Christ to undergo his Passion was now convinced He had to go through it. Later on he would even express his desire to undergo it, too. Which he, in fact, did through his martyrdom.
The third Divine Call that signaled the third conversion took place on Pentecost. But let us look briefly at the events that took place just before Pentecost. Christ called Peter and asked him three times “Do you love me.” It was a demand for Charity. “Feed My Lambs” was their job after the First conversion. “ Take care of My Sheep” was their job after the Second Conversion. And “ Feed My Sheep” was the order for one who has reached the perfection of Charity. And for such a person he must now feed his sheep by teaching them Charity. Though it was an order for all the apostles, at that moment in John 21:15 it was exclusively for Peter and his successors which, in fact, Pope Benedict just did.