4 “So when they had dined, He says to Simon Peter, Simon, [son] of John, do you love me more than these? He says unto Him, Yea, Lord; You know that I love You. He says unto him, Feed my lambs. He says to him again, Simon, [son] of John, do you love me? He says unto Him, Yea, Lord; You know that I love You. He says unto Him, Feed my lambs. He says unto him the third time, Simon, [son] of John, do you love me? Peter was grieved because He said unto him the third time, Do you love me?
And he said unto Him, Lord, You know all things; You know that I love You. He says unto him, Feed my sheep. Verily, verily, I say unto you, When you were young you girded yourself, and walked whither you would, but when you shall be old, you shall stretch forth your hands, and another shall gird you, and carry you whither you will not. And this spoke He, signifying by what death he should glorify God.” Such was the end reached by that denier and lover; elated by his presumption, prostrated by his denial, cleansed by his weeping, approved by his confession, crowned by his suffering, this was the end he reached, to die with a perfected love for the name of Him with whom, by a perverted forwardness, he had promised to die.
He would do, when strengthened by His resurrection, what in his weakness he promised prematurely. For the needful order was that Christ should first die for Peter's salvation, and then that Peter should die for the preaching of Christ. The boldness thus begun by human temerity was an utter inversion of the order that had been instituted by the Truth. Peter thought to lay down his life for Christ, the one to be delivered in behalf of the Deliverer, seeing that Christ had come to lay down His life for all His own, including Peter also, which, you see, was now done.
Now and henceforth a true, because graciously bestowed, strength of heart may be assumed for incurring death itself for the name of the Lord, and not a false one presumptuously usurped through an erroneous estimate of ourselves. Now there is no need that we should any more fear the passage out of the present life, because in the Lord's resurrection we have a foregoing illustration of the life to come. Now you have cause, Peter, to be no longer afraid of death, because He lives whom you mourned when dead, and whom in your carnal love you tried to hinder from dying in our behalf. You dared to step in before the Leader, and you trembled before His persecutor: now that the price has been paid for you, it is your duty to follow the Buyer, and follow Him even to the death of the cross.
You have heard the words of Him whom you have already proved to be truthful; He Himself has foretold your suffering, who formerly foretold your denial.
Source: Tractates on the Gospel of John (New Advent)