John 1:42
“And when Jesus beheld him, He said, 'You are Simon, the son of Jonas; you shall be called Cephas, which is, by interpretation, a stone.'”
2. He begins from this time forth to reveal the things belonging to His Divinity, and to open It out little by little by predictions. So He did in the case of Nathaniel and the Samaritan woman. For prophecies bring men over not less than miracles; and are free from the appearance of boasting. Miracles may possibly be slandered among foolish men,, but nothing of the kind has ever been said of prophecy. Now in the case of Nathaniel and Simon He used this method of teaching, but with Andrew and Philip He did not so. Why was this? Because those (two) had the testimony of John, no small preparation, and Philip received a credible evidence of faith, when he saw those who had been present.
“You are Simon, the son of Jonas.” By the present, the future is guaranteed; for it is clear that He who named Peter's father foreknew the future also. And the prediction is attended with praise; but the object was not to flatter, but to foretell something future. Hear at least in the case of the Samaritan woman, how He utters a prediction with severe reproofs; “You have had,” he says, “five husbands, and he whom thou now hast is not your husband.” So also His Father makes great account of prophecy, when He sets Himself against the honor paid to idols: “Let them declare to you,” says He, “what shall come upon you”; and again, “I have declared, and have saved, and there was no foreign God among you”; and He brings this forward through all prophecy. Because prophecy is especially the work of God, which devils cannot even imitate, though they strive exceedingly. For in the case of miracles there may be delusion; but exactly to foretell the future belongs to that pure Nature alone. Or if devils ever have done so, it was by deceiving the simpler sort; whence their oracles are always easily detected.
But Peter makes no reply to these words; as yet he knew nothing clearly, but still was learning. And observe, that not even the prediction is fully set forth; for Jesus did not say, “I will change your name to Peter, and upon this rock I will build My Church,” but, “You shall be called Cephas.” The former speech would have expressed too great authority and power; for Christ does not immediately nor at first declare all His power, but speaks for a while in a humbler tone; and so, when He had given the proof of His Divinity, He puts it more authoritatively, saying, “Blessed are you, Simon, because My Father has revealed it to you”; and again, “You are Peter, and upon this rock I will build My Church.” Him therefore He so named, and James and his brother He called “sons of thunder.” Why then does He this? To show that it was He who gave the old covenant, that it was He who altered names, who called Abram “Abraham,” and Sarai “Sarah,” and Jacob “Israel.” To many he assigned names even from their birth, as to Isaac, and Samson, and to those in Isaiah and Hosea; but to others He gave them after they had been named by their parents, as to those we have mentioned, and to Joshua the son of Nun. It was also a custom of the Ancients to give names from things, which in fact Leah also has done; and this takes place not without cause, but in order that men may have the appellation to remind them of the goodness of God, that a perpetual memory of the prophecy conveyed by the names may sound in the ears of those who receive it. Thus too He named John early, because they whose virtue was to shine forth from their early youth, from that time received their names; while to those who were to become great at a later period, the title also was given later.
3. But then they received each a different name, we now have all one name, that which is greater than any, being called “Christians,” and “sons of God,” and (His) “friends,” and (His) “Body.” For the very term itself is able more than all those others to rouse us, and make us more zealous for the practice of virtue. Let us not then act unworthily of the honor belonging to the title, considering the excess of our dignity, we who are called Christ's; for so Paul has named us. Let us bear in mind and respect the grandeur of the appellation. For if one who is said to be descended from some famous general, or one otherwise distinguished, is proud to be called this or that man's son, and deems the name a great honor, and strives in every way so as not to affix, by remissness of his own, reproach to him after whom he is called; shall not we who are called after the name, not of a general, nor any of the princes upon earth, nor Angel, nor Archangel, nor Seraphim, but of the King of these Himself, shall not we freely give even our very life, so as not to insult Him who has honored us? Do you not know what honor the royal bands of shield-bearers and spearmen that are about the king enjoy? So let us who have been deemed worthy to be near Him, and much closer, and as much nearer than those just named, as the body is closer to the head than they, let us, I say, use every means to be imitators of Christ.
Source: Homilies on the Gospel of John (New Advent)