Again, ye have heard, &c.— As to oaths, the doctors affirmed, that they were obligatory, according to the nature of the things by which a man swears. See ch. Matthew 23:16. Hence they allowed the use of such oaths in common conversation as they said were not obligatory; pretending that there was no harm in them, because the law which forbad them to forswear themselves, and enjoined them to perform their vows, meant such solemn oaths only, as were of a binding nature. It was this detestablemorality which Jesus condemned in Matthew 5:34-36. By comparing ch. Matthew 23:16 it appears that our Lord is here giving a catalogue of oaths, which, in the opinion of the doctors, were not obligatory. Jesus by no means condemns swearing truly before a magistrate, or upon grave and solemn occasions, because that would have been to prohibit both the best method of ending controversies, Hebrews 6:16 and a high act of religious worship, Deuteronomy 6:13. Isaiah 65:16 an oath being not only a solemn appeal to the divine Omniscience, from which nothing can be hid, but also a direct acknowledgment of God, as the great protector and patron of right, and the avenger of falsehood. But let your communication, says he, be yes, yes; no, no: "Maintain such sincerity and truth in all your words, as will claim the belief of your acquaintance: so that in common conversation, to gain yourselves credit, you should do no more than barely assert or deny any matter, without invoking the name of God at all; for whatsoever is more than these cometh of evil;" or, as it may be translated, cometh of the evil one: 'Εκ του πονηρου. See ch. Matthew 6:13. In common discourse, whatever is more than affirmation or negation, arises either from our own evil heart, or from the temptation of the devil, who prompts men to curse and to swear, that he may lessen their reverence for God, and lead them at length to perjury, even in the most solemn instances; considerations, which shew the evil nature of this sin in the strongest light. We may just observe, that the Jews have a proverb among them to this purpose: "The yea of the just is yea, and their nay, nay:" that is to say, they are sincere, and perform whatever they say or promise. See James 5:12. In whatever sense the last clause be understood,—cometh of evil, it contains a demonstration, that the 34th verse is to be explained with the limitation proposed; for it is evident that oaths were in some cases not only allowed, but required by the Mosaic law. See Exodus 22:11.Leviticus 5:1.Numbers 19:21.Deuteronomy 12:14. So that if Christ's prohibition had here referred to swearing in solemn and judicial cases, he would in these words have charged the divine law with establishing an immorality; which is most absurd to suppose. See Macknight, Doddridge, and Wetstein.
Dr. Campbell well observes, that our Lord is to be considered here, not as prescribing the precise terms wherein we are to affirm or deny, inwhich case it would have suited better the simplicity of his style to say barely, ναι και ου, yes and no, without doubling the words; but as enjoining such an habitual and inflexibleregard to truth, as would render swearing unnecessary. That this manner of converting these adverbs into nouns is in the idiom of the sacred penmen, we have another instance, 2 Corinthians 1:20. For all the promises of God in him are yea, and in him amen; that is, certain and infallible truths.