Psalms 5:6

"The man of blood, and the crafty man, the Lord will abominate." What he said above, "Thou hast hated all that work iniquity, Thou wilt destroy all that speak a lie," may well seem to be repeated here: so that one may refer "the man of blood" to "the worker of iniquity," and "the crafty man" to the "lie." For it is craft, when one thing is done, another pretended. He used an apt word too, when he said, "will abominate." For the disinherited are usually called abominated. Now this Psalm is, "for her who receiveth the inheritance."

"Thou wilt destroy all that speak a lie." For this is the opposite to truth. But lest any one should suppose that any substance or nature is opposite to truth, let him understand that "a lie" has relation to that which is not, not to that which is. For if that which is be spoken, truth is spoken: but if that which is not be spoken, it is a lie. Therefore saith he, "Thou wilt destroy all that speak a lie;" because drawing back from that which is, they turn aside to that which is not. Many lies indeed seem to be for some one's safety or advantage, spoken not in malice, but in kindness: such was that of those midwives in Exodus, who gave a false report to Pharaoh, to the end that the infants of the children of Israel might not be slain. But even these are praised not for the fact, but for the disposition shown; since those who only lie in this way, will attain in time to a freedom from all lying. For in those that are perfect, not even these lies are found. For to these it is said, "Let there be in your mouth, yea, yea; nay, nay; whatsoever is more, is of evil." Nor is it without reason written in another place, "The mouth that lieth slayeth the soul:" lest any should imagine that the perfect and spiritual man ought to lie for this temporal life, in the death of which no soul is slain, neither his own, nor another's. But since it is one thing to lie, another to conceal the truth (if indeed it be one thing to say what is false, another not to say what is true), if haply one does not wish to give a man up even to this visible death, he should be prepared to conceal what is true, not to say what is false; so that he may neither give him up, nor yet lie, lest he slay his own soul for another's body. But if he cannot yet do this, let him at all events admit only lies of such necessity, that he may attain to be freed even from these, if they alone remain, and receive the strength of the Holy Ghost, whereby he may despise all that must be suffered for the truth's sake. In fine, there are two kinds of lies, in which there is no great fault, and yet they are not without fault, either when we are in jest, or when we lie that we may do good. That first kind, in jest, is for this reason not very hurtful, because there is no deception. For he to whom it is said knows that it is said for the sake of the jest. But the second kind is for this reason the more inoffensive, because it carries with it some kindly intention. And to say truth, that which has no duplicity, cannot even be called a lie. As if, for example, a sword be intrusted to any one, and he promises to return it, when he who intrusted it to him shall demand it: if he chance to require his sword when in a fit of madness, it is clear it must not be returned then, lest he kill either himself or others, until soundness of mind be restored to him. Here then is no duplicity, because he, to whom the sword was intrusted, when he promised that he would return it at the other's demand, did not imagine that he could require it when in a fit of madness. But even the Lord concealed the truth, when He said to the disciples, not yet strong enough, "I have many things to say unto you, but ye cannot bear them now:" and the Apostle Paul when he said, "I could not speak unto you as unto spiritual, but as unto carnal." Whence it is clear that it is not blamable, sometimes not to speak what is true. But to say what is false is not found to have been allowed to the perfect.