Numbers 30:4

This chapter is the Torah's law of vows: “he shall not break his word; he shall do according to all that proceeds out of his mouth.” The tradition distinguished the neder, a vow that makes a thing forbidden or dedicated (“this property is korban,” that is, an offering, barred from ordinary use as if given to God), from the shevuah, an oath that binds the person to do or not do something. Around both grew a careful case law: the Mishnah records the substitute formulas people used for korban (konam, konach, konas, Nedarim 1:2), and the tradition itself admitted how far this law outran its text: the rules for releasing vows “fly in the air and have nothing to support them” (Chagigah 1:8).

Two Gospel collisions stand on this chapter. The korban vow that could lock a son's goods away from his own parents is what Jesus confronts in Mark 7:11. And the oath casuistry He attacks in Matthew 5:33-37 and 23:16-22 grew from the practice of swearing by substitutes (heaven, earth, Jerusalem, the Temple) to avoid God's name; the Mishnah itself records that one who administers an oath “in the name of heaven and in the name of earth” leaves the swearer exempt (Shevuot 4:13), exactly the graded-honesty loophole Jesus abolishes with “let your yes be yes.”