Augustine of Hippo : This I know, that even he who teaches that it is meet to tell lies, wishes to be thought to teach a truth. For if it be false which he teaches, who would care to give heed to false doctrine, in which both he deceives that teaches and he is deceived that learns? But if, in order that he may be able to find some disciple, he upholds that he teaches a truth when he teaches that it is meet to lie, how will that lie be of the truth, when the Apostle John reclaimeth, "No lie is of the truth?" It is therefore not true, that it is sometimes right to lie; and that which is not true to no man is at all to be persuaded. — Against Lying Augustine of Hippo : "I write unto you not because ye know not the truth, but because ye know it, and that no lie is of the truth." Behold, we are admonished how we may know antichrist. What is Christ? Truth. Himself hath said "I am the Truth." But "no lie is of the truth." Consequently, all who lie are not yet of Christ. He hath not said that some lie is of the truth, and some lie not of the truth. Mark the sentence. Do not fondle yourselves, do not flatter yourselves, do not deceive yourselves, do not cheat yourselves: "No lie is of the truth." — Ten Homilies on 1 John 3 Bede : I have not written to you because you do not know the truth, etc. For you know the truth of faith and life taught by the anointing of the Spirit, and you do not need to be taught, except that you should persist in what you have begun. — Commentary on the Catholic Epistles Bede : And because every lie is not of the truth. This verse depends on the above, and the sense is: We have not written to you as if you do not know the truth, but as though you know it: and also knowing this, that every lie is not of the truth. Behold, therefore, we are warned how to recognize the Antichrist. Christ says: I am the truth (John 14). But every lie is not from the truth. Therefore, all who lie are not from Christ. He does not say, some lie is from the truth. No one should deceive themselves, let no one delude themselves: every lie is not from the truth. — Commentary on the Catholic Epistles Cyprian : That innocency asks with confidence, and obtains. In the Epistle of John: "If our heart blame us not, we have confidence towards God; and whatever we ask, we shall receive from Him." Also in the Gospel according to Matthew: "Blessed are they of a pure heart, for they shall see God." Also in the twenty-third Psalm: "Who shall ascend into the hill of the Lord? or who shall stand in His holy place? The innocent in hands and of a pure heart." — Treatise XII Three Books of Testimonies Against the Jews Hilary of Arles : You all know the truth because you received it in the rule of faith which you professed at your baptism. — INTRODUCTORY COMMENTARY ON 1 JOHN Oecumenius : "I have not written to you because you do not know the truth, but because you know it, and that no lie is of the truth." Since this is the case, you know that I have not written to you because you do not know the truth, but because you know it. What are these? The last hour, the coming of the Antichrist (1 Jn. 2:18), that all things are full of lies. Therefore, because lies abound, he says: I also say that many antichrists have come. For if Christ is the truth, whom you also know, you have the truth in yourselves, certainly since the liar is contrary to the truth or Christ, he is an antichrist. — Commentary on 1 John