John 21:18-19

When thou wast young, thou girdest thyself. Peter had denied his Master to save his own life. Now that he is reinstated in the old confidence and charged with the Master's work, he is told that he will be called on to die for it. He will be girded, not with a girdle, but with bonds, and he shall be led where he would not, unto death. By what death he should glorify God. These two verses can only be understood as declaring that Peter should die the death of a martyr. John wrote after Peter's death, and may be understood as affirming that he did thus "glorify God". The universal testimony of the ancient Church is that he did thus die. It is asserted that Peter was crucified, a fact that is probable, as he was not a Roman citizen.

Follow me. He had once forsaken Christ through fear of death. Now, with a prospect of violent death before him, he is bidden to resume the Master's work and to follow him. He did this, from this time, faithfully.
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