Calvin's Commentaries, Vol. 31: Matthew, Mark and Luke, Part I, tr. by John King, [1847-50], at sacred-texts.com
33. Again, ye have heard that it was said to the ancients, Thou shalt not perjure thyself: but thou shalt perform to the Lord what thou hast sworn. 34. But I charge you, swear not at all: neither by heaven, for it is the throne of God: 35. Nor by the earth, for it is his footstool: nor by Jerusalem, for it is the city of the great King: 36. Nor shalt thou swear by thy head: for thou canst not make one hair white or black. 37. But your speech shall be, Yes, yes; No, no for what is beyond these comes from evil. 410
33. Thou shalt not perjure thyself This also is not a correction of the law, but a true interpretation of it. For God condemned in the law not only acts of perjury, but lightness in swearing, which lessens the reverence for his name. The man who perjures himself is not the only person who takes the name of God in vain, (Ex 20:7.) He does so, who idly and contemptuously pronounces the name of God on trivial occasions, or in ordinary conversation. While the law condemns every kind of profanation of the name of God the Jews imagined, that the guilt of it lay entirely in acts of perjury. Christ reproves this gross error of supposing that they might, without danger, abuse the name of God, provided they did not swear falsely. We are, no doubt, strictly enjoined to perform to the Lord what we have sworn: for he who, after employing the name of God, cheats and deceives his neighbors, does an injury to God as well as to man. But it is improper to confine to a single part that which has a wider reference. Some consider the word perform as applying to vows, when any thing has been promised to God on account of religion. But this mode of expression applies very well to all promises and engagements, which have been sanctioned by the use of the name of God: for in such cases God is appealed to as guarantee between the parties, to secure their fidelity.
34. Swear not at all Many have been led by the phrase, not at all, to adopt the false notion, that every kind of swearing is condemned by Christ. Some good men have been driven to this extreme rigor by observing the unbridled licentiousness of swearing, which prevailed in the world. The Anabaptists, too, have blustered a great deal, on the ground, that Christ appears to give no liberty to swear on any occasion, because he commands, Swear not at all But we need not go beyond the immediate context to obtain the exposition: for he immediately adds, neither by heaven, nor by the earth Who does not see that those kinds of swearing were added by way of exposition, to explain the former clause more fully by specifying a number of cases? The Jews had circuitous or indirect ways of swearing: and when they swore by heaven, or by earth, or by the altar, (Mt 23:18,) they reckoned it to be next to nothing; and, as one vice springs from another, they defended, under this pretense, any profanation of the name of God that was not openly avowed.
To meet this crime, our Lord declares that they must not swear at all, either in this or that way, either by heaven, or by the earth Hence we conclude, that the particle, at all, relates not to the substance, but to the form, and means, “neither directly nor indirectly.” It would otherwise have been superfluous to enumerate those kinds: and therefore the Anabaptists betray not only a rage for controversy, but gross ignorance, when they obstinately press upon us a single word, and pass over, with closed eyes, the whole scope of the passage. Is it objected, that Christ permits no swearing? I reply: What the expounder of the law says, must be viewed in connection with its design. His statement amounts to this, that there are other ways of “taking the name of God in vain,” besides perjury; and, therefore, that we ought to refrain from allowing ourselves the liberty of unnecessary swearing: for, when there are just reasons to demand it, the law not only permits, but expressly commands us to swear. Christ, therefore, meant nothing more than this, that all oaths are unlawful, which in any way abuse and profane the sacred name of God, for which they ought to have had the effect of producing a deeper reverence.
Neither by heaven It is a mistake to explain these words as meaning, that such forms of swearing are condemned by Christ as faulty, on the ground that we ought to swear by God only. The reasons which he brings forward tend rather to the opposite view, that we swear by the name of God even when we name the heaven, and the earth: because there is no part of the world on which God has not engraved the marks of his glory. But this statement appears not to agree with the precept of the law, in which God expressly commands us to “swear by his name,” (De 6:13;) and likewise with so many passages of Scripture, in which he complains, that injury is done to him, if we swear by creatures. I reply: It is a corruption allied to idolatry, when we appeal to them either as having a right to judge, or authority to prove testimony: for we must look at the object of swearing. It is an appeal which men make to God to revenge falsehood, and to uphold truth. This honor cannot be transferred to another, without committing an outrage on the divine majesty.
For the same reason the Apostle says, that we do not swear in a right manner, unless we swear by the greater, and that it belongs to God alone to swear by himself, (Heb 6:13.) Thus any one who, in ancient times, swore by “Moloch,” (Le 18:21,) or by any other idol, withdrew something of what belonged to God; because they put that idol in the place of God, as possessing an acquaintance with the hearts, and as the judge of the souls of men. And in our own times, those who swear by angels, or by departed saints, take from God what belongs to him, and ascribe to them a divine majesty. The case is different, when men swear by heaven and earth, with a view to the Creator himself: for, in that case, the sanctity of the oath is not founded on creatures, but God alone is appealed to as a witness, by bringing forward the symbols of his glory.
Heaven is called in Scripture (Isa 66:1) the throne of God: not that he dwells in heaven alone, but to teach men to raise their minds upwards, whenever they think of him, and not to form any low or earthly conceptions of him. Again, the earth is called his footstool, (v. 35,) to inform us, that he fills all things, and that no extent of space can contain him. The holiness of Jerusalem (v. 35) depended on his promise. It was the holy city, (Isa 52:1:) because God had selected it to be the seat and residence of his empire. When men swear by their head, (v. 36,) they bring forward their life, which is a remarkable gift of God, as a pledge of their sincerity.
37. 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? 411 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.
“Du mal, ou, malin, ou meschant,” (Jas 5:12;)—”from evil, or, malignant, or wicked.”
“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?”