18 Amen, amen I say to thee, when thou wast younger, thou didst gird thyself, and didst walk where thou wouldst. . . .
Chrysostom: Our Lord having made Peter declare his love, informs him of his future martyrdom. . . . He reminds him of his former life, because, whereas in worldly matters a young man has powers, an old man none; in spiritual things, on the contrary, virtue is brighter, manliness stronger, in old age; age is no hindrance to grace. Peter had all along desired to share Christ’s dangers; so Christ tells him, Be of good cheer; I will fulfill thy desire in such a way, that what thou hast not suffered when young, thou shalt suffer when old. . . . Whence it appears, that he was then neither a young nor an old man, but in the prime of life.
18 . . . But when thou shalt be old, thou shalt stretch forth thy hands, and another shall gird thee, and lead thee whither thou wouldst not. 19 And this he said, signifying by what death he should glorify God. . . .
Augustine: That is, shall be crucified. And to come to this end, Another shall gird you, and carry you where you would not. First He said what would come to pass, secondly, how it would come to pass.
Chrysostom: He says, Whither thou wouldest not, with reference to the natural reluctance of the soul to be separated from the body; an instinct implanted by God to prevent men putting an end to themselves.
Augustine: He who denied and loved, died in perfect love for Him, for Whom he had promised to die with wrong haste. It was necessary that Christ should first die for Peter’s salvation, and then Peter die for Christ’s Gospel.
Scripture from the Douay-Rheims Bible. Commentary from St. Thomas Aquinas, Catena Aurea, Vol. IV (London: Rivington, 1845).