John 15:14

Now sinners are called enemies of God—enemies, that is, of the commands that they do not obey, just as those who obey become friends. The latter are named so from their fellowship; the former from their estrangement, which is freely chosen. For there is neither enmity nor sin without the enemy and the sinner.

There is then no reason, dearest brother, for any one to think that the custom of certain persons is to be followed, who have thought in thee past that water alone should be offered in the cup of the Lord. For we must inquire whom they themselves have followed. For if in the sacrifice which Christ offered none is to be followed but Christ, assuredly it behoves us to obey and do that which Christ did, and what He commanded to be done, since He Himself says in the Gospel, "If ye do whatsoever I command you, henceforth I call you not servants, but friends." And that Christ alone ought to be heard, the Father also testifies from heaven, saying, "This is my well-beloved Son, in whom I am well pleased; hear ye Him." Wherefore, if Christ alone must be heard, we ought not to give heed to what another before us may have I thought was to be done, but what Christ, who is before all, first did. Neither is it becoming to follow the practice of man, but the truth of God; since God speaks by Isaiah the prophet, and says, "In vain do they worship me, teaching the commandments and doctrines of men." And again the Lord in the Gospel repeals this same saying, and says, "Ye reject the commandment of God, that ye may keep your own tradition." Moreover, in another place He establishes it, saying, "Whosoever shall break one of these least commandments, and shall teach men so, he shall be called the least in the kingdom of heaven." But if we may not break even the least of the Lord's commandments, how much rather is it forbidden to infringe such important ones, so great, so pertaining to the very sacrament of our Lord's passion and our own redemption, or to change it by human tradition into anything else than what was divinely appointed! For if Jesus Christ, our Lord and God, is Himself the chief priest of God the Father, and has first offered Himself a sacrifice to the Father, and has commanded this to be done in commemoration of Himself, certainly that priest truly discharges the office of Christ, who imitates that which Christ did; and he then offers a true and full sacrifice in the Church to God the Father, when he proceeds to offer it according to what he sees Christ Himself to have offered.

"Ye are My friends-henceforth I call you not servants, for the servant knoweth not what his lord doeth. Ye are My friends, for all things which I have heard of My Father I have made known unto you."

How then saith He, "I have many things to tell you, but ye cannot bear them now"? By the "all" and the "hearing" He showeth nothing else, but that He uttered nothing alien, but only what was of the Father. And since to speak of secrets appears to be the strongest proof of friendship, "ye have," He saith, "been deemed worthy even of this communion." When however He saith "all," He meaneth, "whatever things it was fit that they should hear." Then He putteth also another sure proof of friendship, no common one.

When the Lord Jesus had commended the love which He manifested toward us in dying for us, and had said, "Greater love hath no man than this, that a man lay down his life for his friends," He added, "Ye are my friends, if ye do whatsoever I command you." What great condescension! when one cannot even be a good servant unless he do his lord's commandments; the very means, which only prove men to be good servants, He wished to be those whereby His friends should be known. But the condescension, as I have termed it, is this, that the Lord condescends to call those His friends whom He knows to be His servants. For, to let us know that it is the duty of servants to yield obedience to their master's commands, He actually in another place reproaches those who are servants, by saying, "And why call ye me, Lord, Lord, and do not the things that I say?" Accordingly, when ye say Lord, prove what you say by doing my commandments. Is it not to the obedient servant that He is yet one day to say, "Well done, thou good servant; because thou hast been faithful over a few things, I will make thee ruler over many things: enter thou into the joy of thy Lord"? One, therefore, who is a good servant, can be both servant and friend.

(viii. de Trin. c. viii) From one and the same love, we love God and our neighbour; but God for His own sake, our neighbour for God's. So that, there being two precepts of love, on which hang all the Law and the Prophets, to love God, and to love our neighbour, Scripture often unites them into one precept. For if a man love God, it follows that he does what God commands, and if so, that he loves his neighbour, God having commanded this. Wherefore He proceeds: Ye are My friends, if ye do whatsoever I command you.

(Tract. lxxxv. 2) Great condescension! Though to keep his Lord's commandments, is only what a good servant is obliged to do, yet, if they do so, He calls them His friends. The good servant is both the servant, and the friend. But how is this? He tells us: Henceforth I call you not servants, for the servant knoweth not what his Lord doeth. Shall we therefore cease to be servants, as soon as ever we are good servants? And is not a good and tried servant sometimes entrusted with his master's secrets, still remaining a servant? (c. 3.). We must understand then that there are two kinds of servitude, as there are two kinds of fear. There is a fear which perfect love casteth out; which also hath in it a servitude, which will be cast out together with the fear. And there is another, a pure (castus) fear, which remaineth for ever. It is the former state of servitude, which our Lord refers to, when He says, Henceforth I call you not servants, for the servant knoweth not what his Lord doeth; not the state of that servant to whom it is said, Well done, thou good servant, enter thou into the joy of thy Lord: (Matt. 25:21) but of him of whom it was said below, The servant abideth not in the house for ever, but the Son abideth ever. Forasmuch then as God hath given us power to become the sons of God, so that in a wonderful way, we are servants, and yet not servants, we know that it is the Lord who doth this. This that servant is ignorant of, who knoweth not what his Lord doeth, and when he doeth any good thing, is exalted in his own conceit, as if he himself did it, and not his Lord; and boasts of himself, not of his Lord.
But I have called you friends, for all things that I have heard of My Father, I have made known unto you.

(Tract. lxxxvi. 1) But how did He make known to His disciples all things that He had heard from the Father, when He forebore saying many things, because He knew they as yet could not bear them? He made all things known to His disciples, i. e. He knew that He should make them known to them in that fulness of which the Apostle saith, Then we shall know, even as we are known. (1 Cor. 13:12) For as we look for the death of the flesh, and the salvation of the soul; so should we look for that knowledge of all things, which the Only-Begotten heard from the Father.

In contrast to the terrors which will sometimes assail those inclined towards obedience and love of virtue He has set the gain of their love towards Him, in order that by the consolations ensuing from this, and by their aiming at what is greater, that which is burdensome may disappear and that which sometimes seems to cause pain sink into insignificance. Sweet is their labour to those who love God, since indeed theirs is a near and rich reward. Who then could conceive any thing greater, and what will he say is more glorious, than to be and be called the friend of Christ? For see how the reward surpasses the very limits of the nature of man. For all things are subject unto Him that made them, according to the saying of the Psalmist; and there is, I suppose, nothing in Creation which has not been subjected to the yoke of slavery, in accordance with the decree becoming the Creator and His work. For the work produced is not on an equality with its producer; and how could it be'? But God, Who is over all, will hold sway over and direct His own works. The universe then being under the yoke of subjection, and putting itself under servitude to God, the Lord leads up His holy ones to a supernatural glory, if they appear willing to work His Will and bring to Him, as an offering that is due, a blameless subjection. Their reward then is glorious and worthy of envy.

(xxvii. Moral.) A friend is as it were a keeper of the soul. He who keeps God's commandments, is rightly called His friend.

There follows: "You are my friends." O how great is the mercy of our Creator! We are not worthy to be servants, and we are called friends. How great is the dignity of men to be friends of God! But you have heard the glory of this dignity; hear also the labor of the struggle: "If you do what I command you." "You are my friends, if you do what I command you." As if He were saying openly: You rejoice at the height; consider by what labors one arrives at the height. Surely when the sons of Zebedee, through the intervention of their mother, sought that one should sit at the right hand of God and the other at the left, they heard: "Can you drink the cup that I am about to drink?" They were already seeking the place of exaltation; the Truth calls them back to the way by which they might come to exaltation. As if it were said: The place of exaltation already delights you, but first let the way of labor exercise you. Through the cup one reaches majesty. If your mind desires what pleases, first drink what causes pain. Thus, thus through the bitter cup of affliction one arrives at the joy of salvation.

He constantly introduces the subject of love, and by these many discourses shows us that the commandment of love is more important than the others and requires great diligence. He also presents the greatest proof of His love.

You are my friends. Here secondly he exhorts to mutual love from the perspective of divine friendship; whence he offers his friendship to those who keep his commandments, so that according to the Lord's precept they may love one another: on account of which he says: You are my friends, if you do what I command you. He promises something great when he promises friendship. Augustine says: "Great is the condescension of the Lord, when he deigned to call us friends," since friend is a name of equality; "for friendship is an agreement with equal goodwill concerning divine and human things." For if wisdom establishes friends of God — Wisdom 7: "She passes into holy souls and establishes friends of God" — how much more does love? This love is proven in works: therefore he says: You are friends, if you do what I command, out of love as friends, not out of fear as servants, because you have not been called into servitude.

2010 Above, our Lord urged us to love our neighbor, based on his example. Here, Christ shows his disciples the benefit conferred upon them which obliges them to imitate him, which is, that he has embraced them in his love. First, he mentions a sign of friendship; secondly, the cause of this friendship (v 16). He gives two signs of friendship: one is found in the disciples; the other in himself (v 15).

2011 The sign in the disciples that they are friends of Christ is that they keep his commandments; he says, You are my friends if you do what I command you. He is saying in effect: Up to now I have urged you to love one another, but now I am speaking and teaching you about your friendship with me.

The statement, you are my friends can be understood in two ways, based on the two ways someone is called a friend. A person is called a friend either because he loves or because he is loved. And what follows, if you do what I command you is true for both meanings of friend. Those who love God keep his commandments, and because a friend is, as Gregory says, in a way the guardian of the other's soul, it is appropriate that one who guards or keeps the will of God in his commandments is called the friend of God. Again, those whom God loves keep his commandments, because by conferring his grace on them he helps them to keep them: for by loving us, God makes us love him: "I love those who love me" (Prv 8:17). It is not they who first loved God, but God makes them lovers by loving them.

2012 Note that keeping the commandments is not the cause of divine friendship but the sign, the sign that both God loves us and that we love God: "Love of her [Wisdom] is the keeping of her laws" (Wis 6:19); "He who says he loves him and does not keep his commandments is a liar" [1 Jn 2:4].