Augustine of Hippo : "For this is the message which we heard from the beginning, that we should love one another." He has made it manifest to us that it is of this he speaks; whoso acts against this commandment, is in that accursed sin, into which those fall who are not born of God. — Ten Homilies on 1 John 5 Bede : For this is the message that you heard from the beginning, that you should love one another. The Lord saying: This is my commandment, that you love one another (John XV). — Commentary on the Catholic Epistles Gregory the Dialogist : But on the other hand, others are not forward to support their needy brethren with things; but only to cherish them with soft words. Which persons the holy preaching of James strongly rebukes, saying, If a brother or sister be naked, and destitute of daily food, and one of you say unto them, Depart in peace, be ye warmed and filled: notwithstanding ye give them not those things which are needful to the body: what shall it profit you? Which persons the Apostle also admonishes, saying, My little children, Let us not love in word, neither in tongue: but in deed and in truth. For our loving affection must always be shewn forth at once by respectfulness of speech, and by the service of almsgiving. — Morals on the Book of Job, Book 21, Section 29 Oecumenius : For this is the message that you heard from the beginning, that we should love one another. Not as Cain, who was of the wicked one and murdered his brother. And why did he murder him? Because his works were evil and his brother's was righteous. Do not marvel, my brethren, if the world hates you. We know that we have passed from death to life because we love the brethren. He who does not love his brother abides in death. Whoever hates his brother is a murderer, and you know that no murderer has eternal life abiding in him. Therefore, having explained these things, he repeats after many points made in between, love for one's neighbor, as if he had treated all that was in between for its sake, since love is also the fullness of everything (Rom. 13:10), and he says: "He who does not love his brother is not of God." But against this, this member is also placed: He is not of God, saying this: For if he who does righteousness is born of God, it follows that he who is therefore born loves his brothers; but he who does not do righteousness, because he does not do it by hating his brothers, is not of God, not in any other way except that he is not born of him. And how he is not of him is shown by saying: "for this is the message that you heard from the beginning." (see Lev. 19:24) What this announcement is, we have already said, both naturally received and through teaching; but also by the legal command to love one's neighbor, as the Lord's command says: "A new commandment I give to you, that you love one another." (Jn. 13:34) The natural command regarding those of the same kind and condition also urges one to do this. Therefore, since there are so many such commands in accordance with the Lord's declaration, whoever keeps and does His word has eternal life and has passed from death to life. (Jn. 5:24) Therefore, let us love our brothers, taking nothing harmful to imitate: for example, if we are hated by the world, let us not also hate our brothers: but let the word of the Lord be more effective in us. For whoever hates his brother is not only cast out from eternal life, but is also a murderer. For it necessarily follows that if he is a murderer, he has no eternal life. Behold Cain, John says, for he too, having hated his brother, murdered him, although he was his brother. But because Cain had evil works, he was the son of the Devil: whereas Abel, by doing righteous works, was called the son of God: the Devil is opposed to God, and evil works to good ones: therefore, Cain, being contrary to his brother, murdered him. Thus, indeed, the course of the discourse was consequent, but blessed John changed the order, always serving what was more pressing. For it was pressing, because he had mentioned the Devil and those who had been adopted by him due to their wicked actions, so as to propose him as an example who, from the beginning of the world, escaped as the wicked son through evil works. — Commentary on 1 John