St. John Chrysostom speaking about the Apostle Peter writes:
“That he was deemed deserving of this office by a great grace of God is a strong proof of his virtue. How strong? Listen to the words Christ spoke to Peter after the resurrection. Christ asked him: ‘Peter, do you love me?’ And Peter replied: ‘Lord, you know I love you.’ What did Christ then say? He did not say: ‘Throw away your money. Fast from food. Live the hard life. Raise the dead. Drive out demons.’ Christ did not bring forward or command any of these things or any other miracle or act of virtue. He passed all these by and said: ‘If you love me, feed my sheep.’ Why did Christ say this? Because he wished to show us not only what is the strongest sign of love for him but also to point out the love which he himself shows for the sheep. So now he makes this the strongest proof which Peter can give of his love for him.
For Christ’s words practically mean: ‘He who loves my sheep loves me.’ And look how many things Christ endured for his flock. He became a man, he took upon himself the form of a servant, he was spat upon, he was slapped in the face, and, finally, he did not refuse to die the most shameful death. For he poured forth his blood on the cross. Therefore, if a man wishes to win esteem in the eyes of Christ, let him show his concern for these sheep, let him seek what is helpful for all, let him be anxious to care for his brothers. God holds no virtuous act in greater esteem.[…] And so it was that Paul, too, said: ‘Be imitators of me as I am of Christ.’ And how, Paul, did you become an imitator of Christ? ‘By pleasing all men in every way, by not seeking my own benefit but the benefit of all men, so that they might be saved.’ Again, in another place, Paul said: ‘Christ did not please himself but please many.’ Therefore, nothing could be so great a mark or sign of the man of faith who loves Christ as would be his care for his brothers and his concern for their salvation. ” (St. John Chrysostom on the Incomprehensible Nature of God, pgs. 170-172)