John 21:18,19 - Coke's Commentary on the Holy Bible

When thou wast young, &c.— St. Peter being thus restored to his apostolic office and dignity, Jesus proceeded to forewarn him of the persecutions, to which he, in particular, would be exposed in the execution of his office, intending thereby to inspire him with courage and constancy; but we do not read a word of that spiritual dignity and authoritywhich his pretended successors have arrogated. When thou wast young, thou girdedst thyself, &c. alluding perhaps to the strength and activitywhich he had now shown in swimming to shore after he had girded his fisher's coat upon him: but, when thou shalt be old, &c. "Instead of that liberty which in youth thou enjoyedst, thou shalt in thine old agebe a prisoner; for thou shalt be bound and carried whither thou wouldest not naturally incline to go, even to those sufferings to which flesh and blood have the strongest aversion." Some have thought, that the words thou shalt stretch forth thy hands, &c. allude to the manner of his death on the cross, and which indeed seems probable from the next words, which the historian delivers as explanatory of those of our Lord, This spake he, signifying by what death he should glorify God. However, the next words of our Lord must plainly be understood to signify, that Peter was to follow him in the kind of his death: "Follow me, and shew that thou art willing to conform to my example, and to follow meeven to the death of the cross." Agreeably hereto, the unanimous voice of antiquity assures us, that St. Peter was crucified, and, as some say, about forty years after this; but the exact time is not known.