S. AURELII AUGUSTINI HIPPONENSIS EPISCOPI DE MENDACIO LIBER UNUS .
4. Quanquam subtilissime quaeratur utrum cum abest voluntas fallendi, absit omnino mendacium.
6. On the other hand, those who say that we must never lie, plead much more strongly, using first the Divine authority, because in the very Decalogue it is written “Thou shall not bear false witness;”4 Exod. xx. 16 under which general term it comprises all lying: for whoso utters any thing bears witness to his own mind. But lest any should contend that not every lie is to be called false witness, what will he say to that which is written, “The mouth that lieth slayeth the soul:”5 Wisdom i. 11. Os quod mentitur. “The mouth that belieth,” E.V., στόμα καταψευδόμενον and lest any should suppose that this may be understood with the exception of some liars, let him read in another place, “Thou wilt destroy all that speak leasing.”6 Psalm v. 6 Whence with His own lips the Lord saith, “Let your communication be yea, yea; nay, nay; for whatsoever is more than these cometh of evil.”7 Matt. v. 37. [See R.V.] Hence the Apostle also in giving precept for the putting off of the old man, under which name all sins are understood, says straightway, “Wherefore putting away lying, speak ye truth.”8 Eph. iv. 25
6. Contra, illi quibus placet nunquam mentiendum, multo fortius agunt, utentes primo auctoritate divina, quoniam in ipso Decalogo scriptum est, Falsum testimonium ne dicas (Id. XX, 16); quo genere complectitur omne mendacium: quisquis enim aliquid enuntiat, testimonium perhibet animo suo. Sed ne quis contendat non omne mendacium falsum testimonium esse appellandum; quid dicturus est ad id quod scriptum est, Os quod mentitur occidit animam (Sap. I, 11)? quod ne quis arbitretur exceptis aliquibus mentientibus posse intelligi, alio loco legat, Perdes omnes qui loquuntur mendacium (Psal. V, 7). Unde 0492 ore suo ipse Dominus: Sit, inquit, in ore vestro, Est, est; Non, non: quod autem amplius est, a malo est (Matth. V, 37). Hinc et Apostolus cum exuendum veterem hominem praeciperet, quo nomine omnia peccata intelliguntur, consequenter ait, in primis ponens, Quapropter deponentes mendacium, loquimini veritatem (Ephes. IV, 25).