(33) By them of old time.--Read, to them of old time, as before. Here, again, the reference is to the letter of the Law as taught by the Rabbis, who did not go beyond it to its wider spirit. To them the Third Commandment was simply a prohibition of perjury, as the Sixth was of murder, or the Seventh of adultery. They did not see that the holy name (Leviticus 19:12) might be profaned in other ways, even when it was not uttered; and they expressly or tacitly allowed (See Philo, De Special. Legg.) many forms of oath in which it was not named, as with the view of guarding it from desecration. Lastly, out of the many forms thus sanctioned (as here and in Matthew 23:16-22) they selected some as binding, and others as not binding, and thus by a casuistry at once subtle, irrational, and dishonest, tampered with men's sense of truthfulness.

Verses 33-37. - Oaths. Matthew only; but cf. Matthew 23:16-22. Verse 33. - By them of old time (ver. 21, note). Thou shalt not forswear thyself (οὐκ ἐπιορκήσεις). These two words are the substance of Leviticus 19:12, which itself (cf. Rashi, in lee.) includes a reference to the third commandment. To them our Lord joins but shalt perform, etc., which is the substance of Deuteronomy 23:23 (cf. Numbers 30:2). (On our Lord's utterance representing the current form of teaching about oaths, cf. ver. 21, note.) This current teaching was the logical deduction from the statements of the Law, and yet the Law had a higher aim.

5:33-37 There is no reason to consider that solemn oaths in a court of justice, or on other proper occasions, are wrong, provided they are taken with due reverence. But all oaths taken without necessity, or in common conversation, must be sinful, as well as all those expressions which are appeals to God, though persons think thereby to evade the guilt of swearing. The worse men are, the less they are bound by oaths; the better they are, the less there is need for them. Our Lord does not enjoin the precise terms wherein we are to affirm or deny, but such a constant regard to truth as would render oaths unnecessary.Again, ye have heard that it hath been said,.... Besides what has been observed, in ver. 21 and 27 you know it has also been said,

by, or to them of old time, what is written in Leviticus 19:12. "And ye shall not swear by my name falsely"; which seems to be referred to, when it is said, "thou shalt not forswear thyself": and is the law forbidding perjury, or false swearing; and was what the Jews were chiefly, if not only concerned about; little regarding the vanity, only the truth of an oath: for they took swearing vainly, to be the same as swearing falsely; wherefore so long as what they swore was truth, they were not careful whether it was of any importance or not: moreover, these men sinned, in that they swore by the creatures, which they thought they might do, and not sin; and when they had so done, were not under obligation to perform; because they made no use of the name of God, to whom only vows and oaths were to be performed, "but shalt perform unto the Lord thine oaths", Numbers 30:2 which they understood of vows only made to the Lord, and not to others; and of oaths, when in his name, and not by others; which they did do, and yet thought themselves not obliged by them.