21:15-19 Our Lord addressed Peter by his original name, as if he had forfeited that of Peter through his denying him. He now answered, Thou knowest that I love thee; but without professing to love Jesus more than others. We must not be surprised to have our sincerity called into question, when we ourselves have done that which makes it doubtful. Every remembrance of past sins, even pardoned sins, renews the sorrow of a true penitent. Conscious of integrity, Peter solemnly appealed to Christ, as knowing all things, even the secrets of his heart. It is well when our falls and mistakes make us more humble and watchful. The sincerity of our love to God must be brought to the test; and it behoves us to inquire with earnest, preserving prayer to the heart-searching God, to examine and prove us, whether we are able to stand this test. No one can be qualified to feed the sheep and lambs of Christ, who does not love the good Shepherd more than any earthly advantage or object. It is the great concern of every good man, whatever death he dies, to glorify God in it; for what is our chief end but this, to die to the Lord, at the word of the Lord?
19. This spake he, signifying by what death he should glorify God—not, therefore, a mere prediction of the manner of his death, but of the honor to be conferred upon him by dying for his Master. And, indeed, beyond doubt, this prediction was intended to follow up his triple restoration:—"Yes, Simon, thou shall not only feed My lambs, and feed My sheep, but after a long career of such service, shalt be counted worthy to die for the name of the Lord Jesus."
And when he had spoken this, he saith unto him, Follow me—By thus connecting the utterance of this prediction with the invitation to follow Him, the Evangelist would indicate the deeper sense in which the call was understood, not merely to go along with Him at that moment, but to come after Him, "taking up his cross."