Feed the sheep whom I bought with my Blood

Zurbarán
Saint Peter appears to Saint Peter Nolasco

The Lord rises from the dead and appears to His disciples. Peter thus sees full of life the One whose death he had dreaded. He realizes not that the Savior was subjected to death, but that in His person death itself was subjected to death. Convinced from this moment by the very example of the risen Lord that death was not something to be feared, he learns to love.

He has the need to love, now that he sees the Lord living after His death; he loves accordingly, he loves in a sure way, sure because he can now follow Him. Therefore, the Lord asks him: "Peter, do you love me?" —  "I love you, Lord," he responds.  As proof of your love, I do not ask you to die for me - I am the one who died for you. What is it then? "Do you love me?" How will you prove to me that you love me? "Do you love me?  —  I love you.  — Feed my sheep."

The Lord repeats himself, twice and thrice: love is thrice confirmed, because fear had thrice denied. ... But after having charged Peter with the care of His sheep, and after having charged Himself of Peter along with His sheep, the Savior predicts Peter's passion. ... You see that one of the duties of the one who is called to feed the sheep of the Lord is to not refuse to die for them.

The good shepherd is the one who gives his life for his sheep. Feed my sheep: whom does He trust with His sheep? Those who are well disposed to take charge of them, or those who are not? And, first of all, who are these sheep that He cares for? Precious sheep, for He bought them not with gold or silver, but with blood. If the owner of a flock wished to entrust it to his servant, he would certainly ask himself if the assets of my servant would be enough to cover the price of the sheep, and he would say: if he loses them, waste them, eats them, he will have the means to pay for them. Finding an assurance in his worthy servant and verifying that the assets of the servant would cover the value of those sheep he bought with his resources, he would then deliver his flock. 

Has not Our Lord Jesus Christ also bought with the price of His blood the sheep that He delivers to His servant? That is why He finds the worthiness of His servant in the blood of his passion.  It is as if He told him: Feed my sheep, I trust you with my sheep. Who are these sheep? Those whom I bought with My Blood. I have died for them - do you love Me? Then you must also die for them.  If a master's servant came to lose his flock, he would pay it back with money. Peter gave his blood for the preservation of the Lord's flock.

Saint Augustine

Sermon on the Feast of Saints Peter and Paul [Sermon 296]