Tractates on the Gospel of John

² I proceed, then, without more delay. When I seek to get into you, that is, into your heart, I preach Christ: were I preaching something else, I should be trying to climb up some other way. Christ, therefore, is my gate to you: by Christ I get entrance, not to your houses, but to your hearts. It is by Christ I enter: it is Christ in me that you have been willingly hearing. And why is it you have thus willingly hearkened to Christ in me? Because you are the sheep of Christ, purchased with the blood of Christ.

You acknowledge your own price, which is not paid by me, but is preached by my instrumentality. He, and only He, was the buyer, who shed precious blood— the precious blood of Him who was without sin. Yet made He precious also the blood of His own, for whom He paid the price of blood: for had He not made the blood of His own precious, it would not have been said, “Precious in the sight of the Lord is the death of His saints.” So also when He says, “The good Shepherd gives His life for the sheep,” He is not the only one who has done such a deed; and yet if those who have done so are His members, He only Himself was the doer of it.

For He was able to do so without them, but whence had they the power apart from Him, who Himself had said, “Without me you can do nothing”? But from the same source we can show what others also have done, for the apostle John himself, who preached the very gospel you have been hearing, has said in his epistle, “Just as Christ laid down His life for us, so ought we also to lay down our lives for the brethren.” “We ought,” he says: He made us debtors who first set the example.

To the same effect it is written in a certain place, “If you sit down to sup at a ruler's table, make wise observation of what is set before you; and put to your hand, knowing that it will be your duty to make similar provision in turn.” You know what is meant by the ruler's table: you there find the body and blood of Christ; let him who comes to such a table be ready with similar provision. And what is such similar provision? As He laid down His life for us, so ought we also, for the edification of others, and the maintenance of the faith, to lay down our lives for the brethren.

To the same effect He said to Peter, whom He wished to make a good shepherd, not in Peter's own person, but as a member of His body: “Peter, do you love me? Feed my sheep.” This He did once, again, and a third time, to the disciple's sorrow. And when the Lord had questioned him as often as He judged it needful, that he who had thrice denied might thrice confess Him, and had a third time given him the charge to feed His sheep, He said to him, “When you were young, you girded yourself, and walked whither you would, but when you shall be old, you shall stretch forth your hands, and another shall gird you, and carry you whither you would not.”

And the evangelist has explained the Lord's meaning: “But this spoke He, signifying by what death he should glorify God.” “Feed my sheep” applies, then, to this, that you should lay down your life for my sheep.