Nicene and Post-Nicene Fathers, Vol. III:
Moral Treatises of St. Augustin: Section 31

31. Thus then what is written, “The mouth that lieth, slayeth the soul;” 2351 of what mouth it speaketh, is the question. For in general when the Scripture speaks of the mouth, it signifies the very seat of our conception 2352 in the heart, where is approved and decreed whatever also by the voice, when we speak the truth, is uttered: so that he lieth with the heart who approveth a lie; yet that man may possibly not lie with the heart, who uttereth other than is in his mind, in such sort that he knows it to be for the sake of avoiding a greater evil that he admitteth an evil, disapproving withal both the one and the other. And they who assert this, say that thus also is to be understood that which is written, “He that speaketh the truth in his heart:” 2353 because always in the heart truth must be spoken; but not always in the mouth of the body, if any cause of avoiding a greater evil require that other than is in the mind be uttered with the voice. And that there is indeed a mouth of the heart, may be understood even from this, that where there is speech, there a mouth is with no absurdity understood: nor would it be right to say, “Who speaketh in his heart,” unless it were right to understand that there is also a mouth in the heart. Though in that very place where it is written, “The mouth that lieth, slayeth the soul,” if the context of the lesson be considered, it may peradventure be taken for no other than the mouth of the heart. For there is an obscure response there, where it is hidden from men, to whom the mouth of the heart, unless the mouth of the body sound therewith, is not audible. But that mouth, the Scripture in that place saith, doth reach to the hearing of the Spirit of the Lord, Who hath filled the whole earth; at the same time mentioning lips and voice and tongue in that place; yet all these the sense permitteth not to be taken, but concerning the heart, because it saith of the Lord, that what is spoken is not hidden from Him: now that which is spoken with that sound which reacheth to our ears, is not hidden from men either. Thus, namely, is it written: “The Spirit of wisdom is loving, and will not acquit an evil-speaker of his lips: for of his reins God is witness, and of his heart a true searcher, and of his tongue a hearer. For the Spirit of the Lord hath filled the whole earth, and that which containeth all things hath knowledge of the voice. Therefore he that speaketh unrighteous things cannot be hid: but neither shall the judgment when it punisheth pass by him. For in the thoughts of the ungodly shall there be interrogation; and the hearing of his words shall come from the Lord, to the punishment of his iniquities. 2354 For the ear of jealousy heareth all things, and the tumult of murmurings will not be hid. Therefore keep yourselves from murmuring, which profiteth nothing, and from backbiting refrain your tongue: because an obscure response will not go into the void. 2355 But the mouth that lieth, slayeth the soul.” 2356 It seems then to threaten them who think that to be obscure and secret, which they agitate and turn over in their heart. And this, it would show, is so clear to the ears of God, that it even calls it “tumult.”

Footnotes

Wisdom 1.11Wisd. i. 11

Conceptaculum

Ps. 15.2Ps. xv. 2

A Domino, “unto the Lord.” E.V.

Obscurum responsum in vacuum non ibit, “There is no word so secret that shall go for nought.” E.V.

Wisdom 1.6-11Wisd. i. 6-11