John Chrysostom
Catena Aurea · Johannesevangelium 21
Verily, verily, I say unto thee, When thou wast young, thou girdedst thyself, and walkedst whither thou wouldest: but when thou shalt be old, thou shalt stretch forth thy hands, and another shall gird thee, and carry thee whither thou wouldest not. This spake he, signifying by what death he should glorify God.
(Hom. lxxxvii) Our Lord having made Peter declare his love, informs him of his future martyrdom; an intimation to us how we should love: Verily, verily, I say unto thee, When thou wast young, thou girdedst thyself, and walkedst whither thou wouldest. 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 fulfil thy desire in such a way, that what thou hast not suffered when young, thou shalt suffer when old: But when thou art old. Whence it appears, that he was then neither a young nor an old man, but in the prime of life.