John 21:19

By what death ... - In these words two things are implied:

1.That Peter would die a violent death; and,

2.That his death would be such as to honor God.

The ancients say that Peter was crucified at Rome, about 34 years after this, with his head downward. Clemens says that he was led to the crucifixion with his wife, and sustained her in her sufferings by exhorting her to remember the example of her Lord. He also adds that he died, not as the philosophers did, but with a firm hope of heaven, and patiently endured the pangs of the cross (Strom. vii.). This declaration of the Saviour was doubtless continually before the mind of Peter, and to the hour of his death he maintained the utmost constancy and fidelity in his cause, thus justifying the appellation which the Lord Jesus gave him - a rock.