Calvin's Commentaries, Vol. 33: Matthew, Mark and Luke, Part III, tr. by John King, [1847-50], at sacred-texts.com
16. Woe to you, blind guides! who say, Whosoever shall swear by the temple, it is nothing; but he who shall swear by the gold of the temple is guilty. 17. Fools, and blind! for which is greater, the gold, or the temple which sanctifieth the gold? 18. And, Whosoever shall swear by the altar, it is nothing; but whosoever shall swear by the gift which is upon it is guilty. 19. Fools, and blind! for which is greater, the gilt, or the altar which sanctifieth the gift? 20. Whosoever therefore shall swear by the altar, sweareth by it, and by all things that are on it. 21. And whosoever shall swear by the temple, sweareth by it, and by him that dwelleth in it. 22. And whosoever shall swear by heaven, sweareth by the throne of God, and by him that sitteth upon it.
Matthew 23:16. Woe to you, blind guides, As ambition is almost always connected with hypocrisy, so the superstitions of the people are usually encouraged by the covetousness and rapacity of pastors. The world has, indeed, a natural propensity to errors, and even draws down upon itself, as if on purpose, every kind of deceit and imposture; but improper modes of worship come to gain a footing only when they are confirmed by the rulers 100 themselves. And it generally happens, that those who possess authority not only, by their connivance, fawn upon errors, because they perceive that they are a source of gain to them, but even assist in fanning the flame. Thus we see that the superstitions of Popery were heightened by innumerable expedients, while the priests opened their mouths for the prey; and even now they daily contrive many things by which they delude still more the foolish multitude. And when minds have once fallen under the darkening influence of the enchantments of Satan, nothing is so absurd or monstrous as not to be eagerly swallowed.
It was on this account that the Jews had more reverence for the gold of the temple, and for the sacred offerings, than for the temple and the altar. But the sacredness of the offerings depended on the temple and the altar, and was only something inferior and accessory. It may readily be believed that this dream proceeded from the scribes and priests, because it was a scheme well fitted for collecting prey. And this was not only a foolish but a highly dangerous error, because it led the people into ridiculous fancies. There is nothing to which men are more prone than to fall away from the pure worship of God: and therefore, under the covering of this veil, it was easy for Satan to withdraw from the contemplation of God those who were too strongly inclined to foolish imaginations. This is the reason why Christ so severely chastises that error. And yet the Papists were not ashamed to prostitute the sacred name of God to a mockery still more detestable; for they reckon it of more importance to touch a morsel of a stinking carcass, than to peruse the sacred volume of the Old and New Testaments, or even to raise their hands towards heaven. And in this way arises a carnal worship of God, by which the proper fear of God is gradually obliterated.
It is nothing. By this phrase he does not mean that they entirely took away the honor of the temple, but he speaks comparatively. For when they represented in extravagant terms the sacredness of offerings, the common people were led to entertain such veneration for them, that the majesty of the temple and of the altar was undervalued, and they reckoned it a less heinous crime to violate it by perjuries than to swear by the sacred offerings with too little reverence.
18. And whosoever shall swear by the altar. Here our Lord does what ought to be done in correcting errors; for he leads us up to the source, and shows, by the very nature of an oath, that the temple is far more valuable than the gifts which are offered in it. He accordingly assumes this principle, that it is not lawful to swear but by the name of God alone. Hence it follows that, whatever forms men may employ in swearing, they must give to God the honor which is due to him; and hence also it follows in what manner and to what extent we are at liberty to swear by the temple, namely, because it is the residence or sanctuary of God; and by heaven, because there the glory of God shines. God permits himself to be called as a witness and judge, by means of such symbols of his presence, provided that he retain his authority unimpaired; for to ascribe any Divinity to heaven would be detestable idolatry. Now so far as God holds out to us a brighter mirror of his glory in the temple than in offerings, so much the greater reverence and sacredness is due to the name of the temple. We now perceive, therefore, in what sense Christ says that we swear by him who inhabits heaven, when we swear by heaven itself. His design is, to direct all forms of swearing to their lawful end and object.
“Quand les prelates les conferment;” — “when the prelates confirm them.”