5:33 Jesus next gave a condensation of several commands in the Old Testament that forbade taking an oath, invoking the Lord's name to guarantee the oath, and then breaking it (Exod. 20:7; Lev. 19:12; Num. 30:2; Deut. 5:11; 6:3; 22:21-23). The rabbis had developed an elaborate stratification of oaths. They taught that swearing by God's name was binding, but swearing by heaven and earth was not binding. Swearing towardJerusalem was binding, but swearing byJerusalem was not. In some cases they even tried to deceive others by appealing to various authorities in their oaths.285
5:34-36 Jesus cut through all the casuistry by saying that if oaths that God intended to guarantee truthfulness in speech become the instruments of deceit, it is better to avoid oaths altogether. Again Jesus got below the external act to the real issue at stake that had been God's concern from the beginning. The way to dispense with false swearing is to avoid all swearing. Righteous people should not need to confirm their statements with an appeal to a higher authority. Their word should be enough (cf. James 5:2).
Jesus explained that whatever a person may appeal to in an oath has some connection with God. Therefore any oath is an appeal to God indirectly if not directly. To say that one could swear by one's own head, for example, and then break his vow, because he did not mention God's name, was shortsighted.
5:37 Jesus' "yes, yes,"and "no, no,"is not the exact terminology He wanted His disciple to use. If He meant that, He would be doing just what He was correcting the rabbis for doing. Rather it means a simple yes or no. The NIV translation gives the sense: "Simply let your Yes' be Yes,' and your No,' No.'"The "evil"at the end of the verse may either be a reference to the devil or it may mean that to go beyond Jesus' teaching on this point involves evil.
Some very conscientious believers have taken Jesus' words literally and have refused to take an oath of any kind even in court. However, Jesus' point was the importance of truthfulness. He probably would not have objected to the use of oaths as a formality in legal proceedings. The Bible records that God Himself swore, not because He sometimes lies but to impress His truthfulness on people (Gen. 9:9-11; Luke 1:68, 73). Jesus testified under oath (26:63-64) as did Paul (Rom. 1:9; 2 Cor. 1:23; 1 Thess. 2:5, 10).
"It must be frankly admitted that here Jesus formally contravenes OT law: what it permits or commands (Deut. 6:13), he forbids. But if his interpretation of the direction in which the law points is authoritative, then his teaching fulfills it."286
