Andreas of Caesarea : The person who loves God keeps his commandments, and loving one's brother is the fulfillment of those commandments. The person who does not love his brother has not kept the commandments and by not keeping them has not loved God. The one who says he loves but does not do so is a liar. — CATENA Augustine of Hippo : "For he that loveth not his brother whom he seeth, how can he love God whom he seeth not? And this commandment have we from Him, that he who loveth God love his brother also." Marvellous fine talk it was, that thou didst say, "I love God," and hatest thy brother! O murderer, how lovest thou God? Hast thou not heard above in this very epistle, "He that hateth his brother is a murderer"? Yea, but I do verily love God, however I hate my brother. Thou dost verily not love God, if thou hate thy brother. — Ten Homilies on 1 John 9 Augustine of Hippo : And now I make it good by another proof. This same apostle hath said, "He gave us commandment that we should love one another." How canst thou be said to love Him whose commandment thou hatest? Who shall say, I love the emperor, but I hate his laws? In this the emperor understands whether thou love him, that his laws be observed throughout the provinces. Our Emperor's law, what is it? "A new commandment give I unto you, that ye love one another." Thou sayest then, that thou lovest Christ: keep His commandment, and love thy brother. But if thou love not thy brother, how canst thou be said to love Him whose commandment thou despisest? — Ten Homilies on 1 John 9 Augustine of Hippo : Brethren, I am never satiated in speaking of charity in the name of the Lord. In what proportion ye have an insatiable desire of this thing, in that proportion we hope the thing itself is growing in you, and casting out fear, that so there may remain that chaste fear which is for ever permanent. Let us endure the world, endure tribulations, endure the stumbling-blocks of temptations. Let us not depart from the way; let us hold the unity of the Church, hold Christ, hold charity. Let us not be plucked away from the members of His Spouse, not be plucked away from faith, that we may glory in His coming: and we shall securely abide in Him, now by faith, then by sight, of whom we have so great earnest, even the gift of the Holy Spirit. — Ten Homilies on 1 John 9 Bede : And this commandment we have from God, etc. For how can you love him whose command you hate? Who is it who says: I love the emperor, but I hate his laws? Not so the true lover of God, but: See (he says) that I have loved your commands, O Lord (Psalm CXVIII). And therefore he confidently adds: Quicken me in your mercy (Ibid.). — Commentary on the Catholic Epistles