Quotes about truth and lying from throughout Christian History. Note: on this page there's a really good modern quote at the bottom. Normally I focus on earlier quotes, but I don't want you to miss the one from 2010 here.
[The true prophets] were entitled to credit because of the miracles which they performed, since they both glorified the Creator, the God and Father of all things, and proclaimed his Son, the Christ [sent] by him. The false prophets, indeed, who are filled with the lying unclean spirit, neither have done nor do. Instead they venture to perform certain wonderful deeds for the purpose of astonishing men, and they glorify the spirits and demons of error. But pray that, above all things, the gates of light may be opened to you; for these things cannot be perceived or understood by all, but only by the man to whom God and his Christ have imparted wisdom. (Dialogue with Trypho, a Jew 7)
"I told you," said [the Angel of Repentance], "that the creatures of God are double because restraint is also double. In some cases restraint has to be exercised; in others there is no need of restraint."
"Make known to me, sir,"I said,"in what cases restraint has to be exercised and in what cases not."
"Restrain yourself in regard to evil, and don't do it; do not exercise restraint in regard to good, but do it. If you exercise restraint in doing good, you will commit a great sin; but if you exercise restraint so that you do not do that which is evil, then you are practicing great righteousness. ..."
"What, sir," I asked, "are the evil deeds from which we must restrain ourselves?"
"Listen," he said. "From adultery, fornication, unlawful revelry, wicked luxury, indulgence in many kinds of food and the extravagance of riches, from boastfulness, haughtiness, insolence, lies, backbiting, hypocrisy, the remembering of wrong, and from all slander. These are the deeds that are most wicked in the lives of men; therefore, the servant of God must restrain himself from all these deeds.
"The one who does not restrain himself from these cannot live to God. ..."
"Are there, sir," I asked, "any other evil deeds?"
"There are," he said, "and many of them, too, from which the servant of God must restrain himself: theft, lying, robbery, false witness, overreaching [ed. note: I don't know what this refers to, and I have no Greek original with which to find out], wicked lust, deceit, pride, boastfulness, and all other vices like these." (Shepherd of Hermas II:8)
The Lord declares that "the devil is a liar from the beginning, and the truth is not in him" [Jn. 8:44]. If, then, he is a liar, and the truth is not in him, then he certainly did not speak truth, but a lie, when he said, “For all these things are delivered to me, and to whomever I wish I give them" [Luke 4:6]. Indeed, he was already accustomed to lying against God for the purpose of leading men astray.
For at the beginning, God had given to man a variety of things for food. He did not command him to eat of one tree only. The Scripture tells us that God said to Adam, "From every tree which is in the garden you shall eat food, but from the tree of knowledge of good and evil, from this you shall not eat, for in the day that you eat of it, you shall die by death" [Gen. 2:16-17]. He then, lying against the Lord, tempted man, as the Scripture says, the serpent saying to the woman, "Has God really said this, 'You shall not eat from every tree of the garden?'" She exposed the falsehood and simply related the command as he had said: "From every tree of the garden we shall eat, but of the fruit of the tree which is in the middle of the garden, God has said, 'You shall not eat of it, nor shall you touch it, lest you die.'" [Gen. 3:1-3]
When he had learned from the woman the command of God, having brought his cunning into play, he finally deceived her by a falsehood, saying, "You shall not die by death;, for God knew that in the day you shall eat of it your eyes shall be opened, and you shall be as gods, knowing good and evil" [Gen. 3:4].
In the first place, then, in the garden of God he disputed about God, as if God was not there, for he was ignorant of the greatness of God. Then, in the next place, after he had learned from the woman that God had said that they would die if they tasted the aforesaid tree ... he uttered the third falsehood, "You shall not die by death" [Gen. 3:4]. But that God was true, and the serpent a liar, was proved by the result, death passed upon those who had eaten. For along with the fruit they also fell under the power of death because they ate in disobedience, and disobedience to God entails death. (Against Heresies V:23:1)
The love of adornment—which is far from caring for virtue, but claims the body for itself—is to be utterly expelled when the love of the beautiful has changed to empty show. Applying things unsuitable to the body, as if they were suitable, gives birth to a practice of lying and a habit of falsehood. It does not show what is decorous, simple, and truly childlike, but what is pompous, luxurious, and effeminate. Such women obscure true beauty, shading it with gold. And they do not know how great their transgression is when they fasten around themselves ten thousand rich chains. As they say that among the barbarians, "Criminals are bound with gold." Such women seem to me to emulate these rich prisoners. (The Instructor II:13)
For the gnostic soul [not a reference to the gnostic religion, but to what Clement calls true gnostics: devout Christians]must be consecrated to the light, stripped of the covering of matter, devoid of the frivolousness of the body and of all the passions—which are acquired through vain and lying opinions—and divested of the lusts of the flesh.
But most men, clothed with what is perishable, like mollusks, and rolled all round in a ball in their excesses, like hedgehogs, entertain the same ideas of the blessed and incorruptible God as of themselves. But it has escaped their notice, though those things are near us, that God has bestowed on us ten thousand things in which he does not share, [such as]: birth, while he is unborn; food, while he needs nothing; growth, while he is always the same; and long life and immortality, while he is immortal and incapable of growing old. (Miscellanies V:11)
The man of proven character in such piety is far from being apt to lie and to swear. For an oath is a decisive affirmation, with the taking of the divine name. For how can he, that is once faithful, show himself unfaithful, so as to require an oath? Shouldn't his life be a sure and decisive oath? He lives, walks, and shows the trustworthiness of his affirmation in an unwavering and sure life and speech.
And if the wrong lies in the judgment of one who does and says [something] and not in the suffering of one who has been wronged, he will neither lie nor commit perjury so as to wrong the Deity, knowing that he by nature is incapable of being harmed. Nor will he lie or commit any transgression for the sake of the neighbor whom he has learned to love, even if he is not on terms of intimacy. Much more, consequently, will he not lie or perjure himself on his own account, since he never with his will can be found doing wrong to himself.
... It's sufficient, then, for him to add to an affirmation or denial the expression, "I'm telling the truth," for confirmation to those who do not perceive the certainty of his answer. For he ought, I think, to maintain a life calculated to inspire confidence towards those outside, so that an oath may not even be asked; and towards himself and those with whom he associates good feeling, which is voluntary righteousness.
... His speaking truth on oath arises from his accord with the truth. This speaking truth on oath, then, is found to be the result of correctness in duties. Where, then, is the necessity for an oath to him who lives in accordance with the extreme of truth?
He, then, that does not ever swear will be far from perjuring himself. And he who does not transgress in what is ratified by agreements will never swear, since the ratification of the violation and of the fulfillment is by actions. Certainly lying and perjury in affirming and swearing are contrary to duty. But he who lives justly, transgressing in none of his duties ... swears truth by his action. As a result, testimony by the tongue is in his case superfluous.
Therefore, persuaded always that God is everywhere, and fearing not to speak the truth, and knowing that it is unworthy of him to lie, he is satisfied with the divine consciousness and his own alone. And so he lies not, nor does he do anything contrary to his agreements. And so he doesn't swear even when asked for his oath; nor does he ever deny, so as to speak falsehood, though he should die by tortures. (Miscellanies VII:8)
Whatever, therefore, [the true gnostic, a term Clement uses to mean a devout Christian] has in his mind, he bears on his tongue, to those who are worthy to hear, speaking as well as living from assent and inclination. For he both thinks and speaks the truth; unless at any time, medicinally, as a physician for the safety of the sick, he may deceive or tell an untruth, according to the Sophists.
To illustrate: the noble apostle circumcised Timothy, even though he loudly declares and writes that circumcision made with hands is of no avail. But in order not to force Hebrews who were reluctant listeners to break away from the synagogue by dragging them all at once away from the law to the circumcision of the heart through faith, he accommodated himself to the Jews, "becoming a Jew, so that he might win everyone" [1 Cor. 9:19].
Therefore, the one who submits to accomodate himself [note: I'm pretty sure this means the person who "adjusts the truth a little,"], but only for the benefit of his neighbors and for [their] salvation ... and who does not take part in any deception out of the peril impending over the just from those who envy them—such a person is certainly not acting out of compulsion.
Instead, for the benefit of his neighbors alone, he will do things which would not have been done by him primarily, if he did not do them on their account. Such a person gives himself for the Church, for the disciples whom he has begotten in faith, for an example to those who are capable of receiving the supreme economy of the philanthropic and God-loving Instructor, for confirmation of the truth of his words, for the exercise of love to the Lord. Such an one is unenslaved by fear, true in word, enduring in labor, never willing to lie by uttered word, and in it always securing sinlessness; since falsehood, being spoken with a certain deceit, is not an inert word, but operates to mischief. (Miscellanies VII:9)
Not any abstract truth, not all abstract truth, not the purest spiritual insight toward any spiritual truth, can make any man free. The truth done, the truth lived … only such truth can make him free. (The Truth in Jesus)
The truth is incontrovertible. Malice may attack it, ignorance may deride it, but in the end; there it is. (unknown)
We first experience the terror of being invalidated when we are small children, but by the time we are 3 or 4 we have learned a way of avoiding it: we have learned how to lie. From then on, whenever we glimpse the faintest possibility that our "selves" might be threatened with annihilation, we lie.
First of all, we lie to ourselves. Why? Because we fear that we do not have the strength and courage to face the truth of our situation. We even lie about lying, preferring to call our lies anything but a lie. We say: "He's in denial" or "She's being economical with the truth". ("Liar, liar: Why deception is our way of life"; from NewScientist magazine)
We aren't ostriches. Their defense mechanism is sticking their head in the ground so they can't see what's coming at them. Our defense mechanism is truth; that's why God gave us such big brains. That's why he reasons with us. (Source: I was there when I wrote this)