Matthew 23:18

Those who work in the fields of the gospel seek the hidden meaning of these passages of Scripture. We are not simply confiscating the higher parts of Scripture but rather looking toward its whole sense. As regards swearing, it is intended as a binding action, seeking to confirm the word concerning which something is sworn.Consider this analogy. Think of the altar as the heart and the temple as the whole of Scripture. The temple of God’s glory, spiritually understood, is the divinely inspired Scripture. The gold refers to the meanings it conveys. To swear is to witness to the Scriptures, as a validation and confirmation of the word we speak. Therefore we ought to profess the whole sense of Scripture as a confirmation of the sense which we invoke in all of our words.
Gold found outside the temple is not sanctified. Rather, that gold which is found in the temple is the measure of that which is outside it. Similarly the meaning which is found outside of the Scriptures is not holy, but it is contained in the meaning of the Scriptures. Only that sense of Scripture is sanctified which can be seen from within the temple itself, that is, within the whole of Scripture. The temple, that is, the reading of the Scriptures, makes a great and venerable sense, just as consecrated gold is valuable. So we ought not to swear by our own intellects to confirm our beliefs, as if we were creating witnesses that could judge according to the truth. But let us explore further the analogy of the temple, the gold and the altar. The altar is the place where a vow is sanctified. The altar in this passage is the heart of a man. What happens in the heart happens deeply within a person. Vows and gifts placed on the altar are clearly those placed upon the human heart. When you begin to pray, you place the vow of your prayer upon your heart, as if you had placed something upon the altar, so that you might offer your prayer to God.
Suppose you are ready to place an offering of psalms upon your heart, so as to offer to God an offering of psalms, accompanying yourself with a harp. Or suppose you are ready to give alms. You make an offering of alms upon your heart, just as if you had placed something on the altar, as you would offer your alms to God. Suppose you have proposed to fast in order to make an offering of your fasting upon your heart, as if you had placed something upon the altar.
In this way the heart of a man makes vows in a holy and venerable way. It is from the heart, that is, the altar, that the vow is offered to God. Therefore it is not possible for the offering of a man to be more honorable than his heart from which the offering is sent up.

In like manner the custom which the Jews had of swearing by the Heaven He reprobates. For they did not, as they supposed, avoid the danger of taking an oath by God, because, Whose sweareth by heaven, sweareth by the throne of God, and by him that sitteth thereon.

Now an oath is in confirmation of somewhat that has been spoken. The oath here then may signify testimony of Scripture which we produce in confirmation of that word which we speak. So that Divine Scripture is the temple of God, the gold is the meaning which it contains. As the gold which is outside the Temple is not sanctified, so all thoughts which are without divine Scripture, however admirable they may seem, are not hallowed. We ought not therefore to bring any speculations of our own for the confirmation of doctrine, unless such as we can show are hallowed by being contained in divine Scripture. The altar is the human heart, which is the chief thing in man. The offerings and gifts that are hid upon the altar, are every thing which are done in the heart, as to pray, to sing, to do alms, to fast. Every offering of a man then is sanctified by his heart, by which the offering is made. There cannot therefore be a more honourable offering than the heart of man, out of which the offering proceeds. If then one's conscience does not smite him, he has confidence towards God, not by reason of his gifts, but so to speak because he has rightly ordered the altar of his heart. Thirdly, we may say that over the temple, that is over every Scripture, and over the altar, that is over every heart, there is a certain meaning which is called the Heaven, the throne of God Himself, in which we shall be able to see the things that are revealed face to face, when that which is perfect is come.

For since Christ is come, reliance upon the Law is vain; for not Christ by the Law, but the Law by Christ, is sanctified, in whom it rests as on a seat or throne; so are they fools and blind, who, overlooking the sanctifier, pay honour to the things sanctified.

As by making broad phylacteries and fringes they sought after the reputation of sanctity, and made this again a means of gain, so now He charges them with being teachers of wickedness by their fraudulent pretence of tradition. For when in any dispute or quarrel, or ambiguous cause, one swore by the temple, and was afterwards convicted of falsehood, he was not held guilty. This is what is meant by that, Whosoever shall swear by the temple, it is nothing, that is, he owes nothing, But if he had sworn by the gold, or by the money which was offered to the Priests in the temple, he was immediately compelled to pay down that by which he had sworn.

Again, if one swore by the altar, none held him guilty of perjury; but if he swore by the gift or the victims or the other things which are offered to God upon the altar, this they exacted most rigorously. And all this they did not out of fear of God, but out of covetousness. Thus the Lord charges them with both folly and fraud, inasmuch as the altar is much greater than the victims which are sanctified by the altar.

(Verse 16 onwards) Woe to you, blind guides, who say, 'Whoever swears by the temple is nothing, but whoever swears by the gold of the temple is bound by his oath.' Fools and blind! For which is greater, the gold or the temple that sanctifies the gold? And, 'Whoever swears by the altar is nothing, but whoever swears by the gift that is on it is obligated.' Blind! For which is greater, the gift or the altar that sanctifies the gift? Therefore, whoever swears on the altar, swears on it and on all things that are above it. And whoever swears in the temple, swears in it and in him who dwells in it. And whoever swears in heaven, swears on the throne of God and on him who sits on it. Above, as it seemed to us, we have explained what the tradition of the Pharisees meant, saying: Whatever gift is from me will benefit you: now the double tradition of the Pharisees, enticing to one occasion of greed, is condemned, so that they may be proved to do everything for gain and not for the fear of God. For just as in the phylacteries and fringes, by enlarged expectations of holiness, it was trying to capture glory, and was seeking gains through the opportunity of glory, so another tradition found fault with the teachers of impiety. If anyone were to swear in the temple during a dispute, or in some argument, or in a doubtful case, and later be convicted of lying, they were not held accountable for the crime. But if they were to swear on gold and money, which was offered to the priests in the temple, they were immediately compelled to fulfill what they had sworn. Again: If anyone swore upon the altar, no one held him guilty of perjury; but if he swore falsely on a gift, or on offerings, that is, on victims and on fine flour and on the rest, which are offered to God upon the altar, these were most diligently sought after. Therefore, the Lord reproached them both for foolishness and deceit, because the temple is much greater than the gold that is sanctified by the temple, and the altar is greater than the offerings that are sanctified by the altar. But they did it not out of fear of God, but out of greed for riches.

(Quæst. Ev. i. 34.) The temple and altar we may also understand of Christ Himself; the gold and the gifts, of the praise and sacrifice of prayer which we offer in Him and through Him. For not He by them, but they by Him, are sanctified.

The temple pertains to God's glory, and to man's spiritual salvation, but the gold of the temple though it pertains to the glory of God, yet does it more so to the delight of man, and the profit of the Priests. The Jews then pronounced the gold which delighted them, and the gifts which fed them, to be more holy than the temple, that they might make men more disposed to offer gifts, than to pour out prayers in the temple. Whence the Lord suitably reproves them in these words. Yet have some Christians at present an equally foolish notion. See, they say, in any suit if one swear by God, it seems nought; but if one swear by the Gospel, he seems to have done some great thing. To whom we shall say in like manner, Ye fools and blind! the Scriptures were written because of God, God is not because of the Scriptures. Greater therefore is God, than what is hallowed by Him.

(non occ.) And lest their infatuation should go so far, that they should affirm that the gold was more holy than the temple, and the gift than the altar, He argues on another ground, that in the oath which is sworn by the temple and the altar is contained the oath by the gold or by the gift.

(ord.) For whoso swears by the creature that is subject, swears by the Divinity that rules over the creation.