Note 17 at Mt 23:20: In the Hebrew way of thinking, an oath was a solemn appeal to the truth of an affirmation or promise. Invoking God's name in an oath carried the idea of the all-knowing, all-seeing God watching over people's words with the most serious consequences for those who broke them (Ge 31:49-53; 1Sa 12:5, and 19:6). The Apostle Paul used the same kind of Hebrew thinking when he called upon God as a witness to the truthfulness of his statements (2Co 1:23, Ga 1:20, and Php 1:8).

The Law of Moses established guidance concerning oaths in several situations: the loss of one's personal property (Ex 22:10-11), the finding of lost possessions (Le 6:3), when a woman was suspected of unfaithfulness to her husband (Nu 5:11-31), and the misuse of swearing and concealing the truth (Le 5:1). The Old Testament also cautioned against swearing lightly with the solemn warning of Ec 5:5, "Better is it that thou shouldest not vow, than that thou shouldest vow and not pay."

Although Jesus accepted the credibility of a claim confirmed by an oath (Mt 26:63-64), His teaching denounced a double standard accepted by some Jews that one's word had to be confirmed by an oath. For Christ's followers, one's life and word should be as sacred as an oath (Mt 5:37). Under His rule, oaths should be an unnecessary thing (Mt 5:34-37), for Christians carry Christ's name in all that they say and do (1Co 6:20).