1 It is no unimportant question why the Lord, when He manifested Himself for the third time to the disciples, said unto the Apostle Peter, “Follow me;” but of the Apostle John, “Thus I wish him to remain till I come, what is that to you?” To the discussion or solution of this question, according as the Lord shall grant us ability we devote the last discourse of this work. When the Lord, then, had announced beforehand to Peter by what death he was to glorify God, “He says unto him, Follow me.
Then Peter, turning about, sees the disciple whom Jesus loved following; who also leaned on His breast at supper, and said, Lord, which is he that shall betray You? Peter, therefore, seeing him, says to Jesus, Lord, and what [of] this man? Jesus says unto him, Thus do I wish him to remain till I come, what is that to you? You follow me. Then went this saying abroad among the brethren, that that disciple dies not: yet Jesus said not unto him, He dies not; but, Thus do I wish him to remain till I come, what is that to you?”
You see the great extent in this Gospel of a question which, by its depth, must exercise in no ordinary way the mind of the inquirer. For why is it said to Peter, “Follow me,” and not to the others who were likewise present? Surely the disciples followed Him also as their Master. But if it is to be understood only in reference to his suffering, was Peter the only one that suffered for the truth of Christianity? Was there not present there among those seven, another son of Zebedee, the brother of John, who, after His ascension, is plainly recorded to have been slain by Herod? But some one may say that, as James was not crucified, it was properly enough said to Peter, “Follow me,” inasmuch as he underwent not only death, but, like Christ, even the death of the cross.
Be it so, if no other explanation can be found that is more satisfactory. Why, then, was it said of John, “Thus do I wish him to remain till I come, what is that to you?” and the words repeated, “You follow me,” as if that other, therefore, were not to follow, seeing He wished him to remain till He comes. Who can readily believe that anything else was meant than what the brethren who lived at the time believed, namely, that that disciple was not to die, but to abide in this life till Jesus came? But John himself removed such an idea, by giving a flat contradiction to the report that the Lord had said so. For why should he add, “Jesus says not, He dies not,” save to prevent what was false from taking hold of the hearts of men?
Source: Tractates on the Gospel of John (New Advent)