But your speech shall be, Yes, yes; No, no Christ now prescribes, in the second place, a remedy; which is, that men act towards each other sincerely and honestly: for then simplicity of speech will have quite as much weight as an oath has among those who are not sincere. Now, this is certainly the best way of correcting faults, to point out the sources from which they spring. Whence comes the great propensity to swearing, but from the great falsehood, the numerous impositions, the unsteady and light conduct, so that hardly any thing is believed? [1] Fairness and honesty in our words are, therefore, demanded by Christ, that there may be no longer any occasion for an oath. "Yes, yes; No, no." This repetition means, that we ought to abide by our words, so that all may be convinced of our honesty. Now, as this is the true and lawful method of proceeding, when men have nothing on their tongue but what is in their heart, Christ declares, that what is beyond these comes from evil I do not approve of the exposition of these words which some have given, that the criminality of swearing ought to be charged on the man who does not give credit to what another says. Christ teaches us, in my opinion, that it originates in the wickedness of men, that they are compelled to swear: for, if honesty prevailed among men, if they were not inconsistent and hypocritical, they would maintain that simplicity which nature dictates. And yet it does not follow, that it is unlawful to swear, when necessity demands it: for many things are proper in themselves, though they have had a wicked origin.

Footnotes

1 - "D'ou vient une si grande legerete en sermens, sinon qu'entre tout de mensonges, tromperies, inconstance et babil, on ne sait qui croire, ni a qui se fier?" -- "Whence comes so great a lightness about oaths, but that among so many lies and impositions, and so much unsteadiness and trifling, one does not know whom to believe or whom to trust?"

But let your communication - Your word; what you say.
Be, Yea - Yes. This does not mean that we should always use the word "yea," for it might as well have been translated "yes"; but it means that we should simply affirm or declare that a thing is so.
More than these - More than these affirmations.
Cometh of evil - Is evil. Proceeds from some evil disposition or purpose. And from this we may learn:
1. That profane swearing is always the evidence of a depraved heart. To trifle with the name of God, or with any of his works, is itself most decided proof of depravity.
2. That no man is believed any sooner in common conversation because he swears to a thing. When we hear a man swear to a thing, it is pretty good evidence that he knows what he is saying to be false, and we should be on our guard. He that will break the third commandment will not hesitate to break the ninth also. And this explains the fact that profane swearers are seldom believed. The man who is always believed is he whose character is beyond suspicion in all things, who obeys all the laws of God, and whose simple declaration, therefore, is enough. A man that is truly a Christian, and leads a Christian life, does not need oaths and profaneness to make him believed.
3. It is no mark of a gentleman to swear. The most worthless and vile. the refuse of mankind, the drunkard and the prostitute, swear as well as the best dressed and educated gentleman. No particular endowments are requisite to give finish to the art of cursing. The basest and meanest of mankind swear with as much tact and skill as the most refined, and he that wishes to degrade himself to the very lowest level of pollution and shame should learn to be a common swearer. Any person has talents enough to learn to curse God and his fellowmen, and to pray - for every man who swears prays - that God would sink him and others into hell. No profane person knows but that God will hear his prayer, and send him to the regions of woe.
4. Profaneness does no one any good. Nobody is the richer, or wiser, or happier for it. It helps no one's morals or manners. It commends no one to any society. The profane man must be, of course, shut out from female society, and no refined conversation can consist with it. It is disgusting to the refined; abominable to the good; insulting to those with whom we associate; degrading to the mind; unprofitable, needless, and injurious in society; and awful in the sight of God.
5. God will not hold the profane swearer guiltless. Wantonly to profane His name, to call His vengeance down, to curse Him on His throne, to invoke damnation, is perhaps of all offences the most awful. And there is not in the universe more cause of amazement at His forbearance, than that God does not rise in vengeance, and smite the profane swearer at once to hell. Verily, in a world like this, where His name is profaned every day, and hour, and moment by thousands, God shows that He is slow to anger, and that His mercy is without bounds!

Let your communication be, Yea, yea; Nay, nay - That is, a positive affirmation, or negation, according to your knowledge of the matter concerning which you are called to testify. Do not equivocate; mean what you assert, and adhere to your assertion. Hear what a heathen says on this subject: -
Εχθρος γαρ μοι κεινος ὁμως αιδαο πυλησιν,
Ος χ'ετερον μεν κευθει ενι φρεσιν, αλλο δε βαζει.
Hom. Il. ix. 312
"He whose words agree not with his private thoughts is as detestable to me as the gates of hell."
See on Joshua 2 (note) at the end.
See the subject of swearing particularly considered in the note at the conclusion of Deuteronomy 6 (note).
Whatsoever is more than these - That is, more than a bare affirmation or negation, according to the requirements of Eternal Truth, cometh of evil; or, is of the wicked one - εκ του πονηρου εϚιν, i.e. the devil, the father of superfluities and lies. One of Selden's MSS. and Gregory Nyssen, a commentator of the fourth century, have εκ του διαβολου εϚιν, is of the devil.
That the Jews were notoriously guilty of common swearing, for which our Lord particularly reprehends them, and warns his disciples against, and that they swore by heaven, by earth, by Jerusalem, by their head, etc., the following extracts, made by Dr. Lightfoot from their own writings, amply testify: -
"It was customary and usual among them to swear by the creatures. 'If any swear by heaven, by earth, by the sun, etc., although the mind of the swearer be, under these words, to swear by Him who created them, yet this is not an oath. Or, if any swear by some of the prophets, or by some of the books of the Scripture, although the sense of the swearer be to swear by Him that sent that prophet, or that gave that book, nevertheless, this is not an oath. Maimonides.'
"If any adjure another by heaven or earth, he is not guilty. Talmud.
"They swore by Heaven, השמים כן הוא hashshamayim, ken hu, 'By heaven, so it is.' Bab. Berac.
"They swore by the Temple. 'When turtles and young pigeons were sometimes sold at Jerusalem for a penny of gold, Rabban Simeon ben Gamaliel said, המעו הוה By this habitation (that is, by this Temple) I will not rest this night, unless they be sold for a penny of silver.' Cherituth, cap. i.
"R. Zechariah ben Ketsab said, המעו הוה 'By this Temple, the hand of the woman departed not out of my hand.'
R. Jochanan said, היכלא 'By the Temple, it is in our hand, etc.' Ketuboth and Bab. Kidushin.
"Bava ben Buta swore by the Temple in the end of the tract Cherithuth, and Rabban Simeon ben Gamaliel in the beginning, וזה מנהג כישראל And so was the custom in Israel. - Note this, so was the custom.
Jucas. fol. 56.
"They swore by the city Jerusalem. R. Judah saith, 'He that saith, By Jerusalem, saith nothing, unless with an intent purpose he shall vow towards Jerusalem.' Where also, after two lines coming between those forms of swearing and vowing, are added, ירושלם לירושלם בירושלם היכל להיכל בהיכל 'Jerusalem, For Jerusalem, By Jerusalem. - The Temple, For the temple, By the temple. - The Altar, For the altar, By the altar. - The Lamb, For the Lamb, By the Lamb. - The Chambers of the Temple, For the chambers of the temple, By the chambers of the temple. - The Word, For the Word, By the Word. - The Sacrifices on Fire, For the sacrifices on fire, By the sacrifices on fire. - The Dishes, For the dishes, By the dishes. - By all these things, that I will do this to you.' Tosapht. ad. Nedarim.
"They swore by their own Heads. 'One is bound to swear to his neighbor, and he saith, ריד לי כתיי ראשך Vow (or swear) to me by the life of thy head, etc. Sanhedr. cap. 3.
"One of the holiest of their precepts relative to swearing was this: 'Be not much in oaths, although one should swear concerning things that are true; for in much swearing it is impossible not to profane.' Tract. Demai." - See Lightfoot's Works, vol. ii. p. 149.
They did not pretend to forbid All common swearing, but only what they term Much. A Jew might swear, but he must not be too abundant in the practice. Against such permission, our Lord opposes his Swear Not At All! He who uses any oath, except what he is solemnly called by the magistrate to make, so far from being a Christian, he does not deserve the reputation, either of decency or common sense. In some of our old elementary books for children, we have this good maxim: "Never swear: for he that swears will lie; and he that lies will steal; and, if so, what bad things will he not do!" Reading Made Easy.

But let your communication be, (t) Yea, yea; Nay, nay: for whatsoever is more than these cometh of (u) evil.
(t) Whatever you affirm, affirm it alone, and whatever you deny, deny it alone without any more words.
(u) From an evil conscience, or from the devil.

But let your communication be yea, yea,.... That is, let your speech, in your common conversation, and daily business of life, when ye answer to anything in the affirmative, be "yea"; and when ye answer to anything in the negative, "nay": and for the stronger asseveration of the matter, when it is necessary, double these words; but let no oaths be joined unto them: this is enough; a righteous man's yea, is yea, and his no, is no; his word is sufficient. Hence it appears, that our Lord is here speaking of rash swearing, and such as was used in common conversation, and is justly condemned by him. The Jews have no reason to reject this advice of Christ, who often use and recommend the same modes of expression. They endeavour to raise the esteem of their doctors and wise men, by saying, that their words, both in doctrines and dealings with men, are "yea, yea" (y). One of their (z) commentators on the word "saying", in, Exodus 20:1 makes this observation;
"hence we learn, that they used to answer, "concerning yea, yea, and concerning nay, nay".''
This way of speaking, they looked upon equivalent to an oath; yea, they affirm it was one.
"Says R. Eliezer (a), , "nay is an oath; yea is an oath", absolutely; "nay" is an oath, as it is written, Genesis 9:11 and Isaiah 54:9. But that "yea" is an oath, how does it appear? It is concluded from hence, that "nay" is an oath; saith Rabba, there are that say "nay, nay", twice; and there are that say "yea, yea", twice; as it is written, Genesis 9:11 and from hence, that "nay" is twice, "yea" is also twice said.''
The gloss upon it is,
"he that says either "nay, nay", twice, or "yea, yea", twice; lo! it is "as an after oath", which confirms his words.''
For whatsoever is more than these, cometh of evil: that is, whatever exceeds this way of speaking and conversation, in the common affairs of life, is either from the devil, who is the evil one, by way of eminency; or from the evil heart of man, from the pride, malice, envy, &c. that are in it.
(y) T. Bab. Moed Katon, fol. 20. 1. Maimon. Hilch. Dayot. c. 5. sect. 13. (z) R. Song. Jarchi, in Exod. xx. 1. (a) T. Bab. Shebuot, fol. 36. 1. Vid. Maimon. Hilch. Shebuot, c. 2. sect. 1.

But let your communication--"your word," in ordinary intercourse, be,
Yea, yea; Nay, nay--Let a simple Yes and No suffice in affirming the truth or the untruth of anything. (See James 5:12; 2-Corinthians 1:17-18).
for whatsoever is more than these cometh of evil--not "of the evil one"; though an equally correct rendering of the words, and one which some expositors prefer. It is true that all evil in our world is originally of the devil, that it forms a kingdom at the head of which he sits, and that, in every manifestation of it he has an active part. But any reference to this here seems unnatural, and the allusion to this passage in the Epistle of James (James 5:12) seems to show that this is not the sense of it: "Let your yea be yea; and your nay, nay; lest ye fall into condemnation." The untruthfulness of our corrupt nature shows itself not only in the tendency to deviate from the strict truth, but in the disposition to suspect others of doing the same; and as this is not diminished, but rather aggravated, by the habit of confirming what we say by an oath, we thus run the risk of having all reverence for God's holy name, and even for strict truth, destroyed in our hearts, and so "fall into condemnation." The practice of going beyond Yes and No in affirmations and denials--as if our word for it were not enough, and we expected others to question it--springs from that vicious root of untruthfulness which is only aggravated by the very effort to clear ourselves of the suspicion of it. And just as swearing to the truth of what we say begets the disposition it is designed to remove, so the love and reign of truth in the breasts of Christ's disciples reveals itself so plainly even to those who themselves cannot be trusted, that their simple Yes and No come soon to be more relied on than the most solemn asseverations of others. Thus does the grace of our Lord Jesus Christ, like a tree cast into the bitter waters of human corruption, heal and sweeten them.
Same Subject--Retaliation (Matthew 5:38-42). We have here the converse of the preceding lessons. They were negative: these are positive.

Let your speech be, Yea, yea. All foolish appeals are forbidden. A simple statement is all Christ permits. All beyond is evil, "and cometh of evil." Indeed, it makes one doubt the truth of him who has to confirm every assertion by an oath.

Let your conversation be yea, yea; nay, nay - That is, in your common discourse, barely affirm or deny.