Again, you have heard that it has been said by them of old time, You shall not perjure yourself, but shall perform unto the Lord your oaths:
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Augustine of Hippo
AD 430
The righteousness of the Pharisees is not to forswear oneself; and this is confirmed by Him who gives the command not to swear, so far as relates to the righteousness of the kingdom of heaven. For just as he who does not speak at all cannot speak falsely, so he who does not swear at all cannot swear falsely. But yet, since he who takes God to witness swears, this section must be carefully considered, lest the apostle should seem to have acted contrary to the Lord's precept, who often swore in this way, when he says, Now the things which I write unto you, behold, before God I lie not; and again, The God and Father of our Lord Jesus Christ, which is blessed for evermore, knows that I lie not. Of like nature also is that asseveration, For God is my witness, whom I serve with my spirit in the gospel of His Son, that without ceasing I make mention of you always in my prayers. Unless, perchance, one were to say that it is to be reckoned swearing only when something is spoken of by which one swears; so that he has not used an oath, because he has not said, by God; but has said, God is witness. It is ridiculous to think so; yet because of the contentious, or those very slow of apprehension, lest any one should think there is a difference, let him know that the apostle has used an oath in this way also, saying, By your rejoicing, I die daily. And let no one think that this is so expressed as if it were said, Your rejoicing makes me die daily; just as it is said, By his teaching he became learned, i.e. by his teaching it came about that he was perfectly instructed: the Greek copies decide the matter, where we find it written, Νὴ τὴν καύχησιν ὑμετέραν, an expression which is used only by one taking an oath. Thus, then, it is understood that the Lord gave the command not to swear in this sense, lest any one should eagerly seek after an oath as a good thing, and by the constant use of oaths sink down through force of habit into perjury. And therefore let him who understands that swearing is to be reckoned not among things that are good, but among things that are necessary, refrain as far as he can from indulging in it, unless by necessity, when he sees men slow to believe what it is useful for them to believe, except they be assured by an oath.
