5 And that you may know that it is this perfect charity which that man violates not, and against which that man sins not, who is born of God; this is what the Lord says to Peter; “Peter do you love me?” And he answers, “I love.” He says not, If you love me, show kindness to me. For when the Lord was in mortal flesh, He hungered, He thirsted: at that time when He hungered and thirsted, He was taken in as a guest; those who had the means, ministered unto Him of their substance, as we read in the Gospel.
Zacchæus entertained Him as his guest: he was saved from his disease by entertaining the Physician. From what disease? The disease of avarice. For he was very rich, and the chief of the publicans. Mark the man made whole from the disease of avarice: “The half of my goods I give to the poor; and if I have taken any thing from any man, I will restore him fourfold.” That he kept the other half, was not to enjoy it, but to pay his debts. Well, he at that time entertained the Physician as his guest, because there was infirmity of the flesh in the Lord, to which men might show this kindness; and this, because it was His will to grant this very thing to them that did Him kind service; for the benefit was to them that did the service, not to Him.
For, could He to whom angels ministered require these men's kindness? Not even His servant Elias, to whom He sent bread and flesh by the ravens upon a certain occasion had need of this; and yet that a religious widow might be blessed, the servant of God is sent, and he whom God in secret did feed, is fed by the widow. But still, although by the means of these servants of God, those who consider their need get good to themselves, in respect of that reward most manifestly set forth by the Lord in the Gospel: “He that receives a righteous man in the name of a righteous man shall receive a righteous man's reward: and he that receives a prophet in the name of a prophet shall receive a prophet's reward: and whosoever shall give to drink unto one of these little ones a cup of cold water only in the name of a disciple, verily I say unto you, He shall in no wise lose his reward:” although, then, they that do this, do it to their own good: yet neither could this kind office be done to Him when about to ascend into Heaven.
What could Peter, who loved Him, render unto Him? Hear what. “Feed my sheep:” i.e. do for the brethren, that which I have done for you. I redeemed all with my blood: hesitate not to die for confession of the truth, that the rest may imitate you.
Source: Homilies on the First Epistle of John (New Advent)