But I say to you, do not take an oath at all …
Jesus follows His radically intensified explanation of the sixth and seventh commandments (on murder and adultery) by moving outside of the Decalogue to deal with another matter, which like divorce, was on the front of the minds of first Century Jews. Jesus’ quotation of the law summarizes a series of related passages on oaths (Lev 19:12, Num 30:2, Deut 23:21-23). While not directly from the Decalogue, His teaching does lend a fuller understanding to both the third and ninth commandments against taking the name of the Lord in vain, and bearing false witness (Ex 20:7, 16).
Just like the Pharisees misused the text in Deuteronomy 24:1-4 as a license to grant divorces for all sorts of frivolous reasons, they saw the regulation on oaths as a justification for a diversity of oaths. Judaism had accumulated quite an elaborate hierarchy of laws concerning oaths which became the subject of an entire tractate of the Mishnah (Judaism’s oral law). The extensive and even superstitious use of vows implied that a person’s word may not be dependable unless accompanied by some sort of swearing. While the Mosaic Law clearly forbade irreverent oaths, broken vows, and using the Lord’s name in vain, many Jews at the time considered swearing by “heaven,” “earth,” “Jerusalem,” or “one’s head,” as less binding than swearing “by God;” so by manipulating the words of their oaths, they provided themselves a way of not being faithful to their word. The cunning Jewish distinctions and Jesus’ severe rebuke of what amounted to nothing less than “sanctified lying” can be seen later in Matthew’s Gospel (23:16-22). Jesus taught the error of this practice by revealing the Jewish people’s failure to see God in everything. A man who is truly righteous needs no oaths because he knows that every statement he utter, is made in the very presence of God.
This text has historically been applied in a variety of different ways. Some Christian groups and cults have sought to codify Jesus’ teaching, forcing its application in areas that perhaps it was never meant to apply to. But to codify Jesus’ teaching is to fall into the same error as the Talmudic Rabbis who Jesus is essentially rebuking in this section of the Sermon on the Mount. Jesus’ “rules,” reach far beyond any external regulation; once again, we find the root of the solution to oath taking in the heart. In essence Jesus directs us to be a faithful and honest people who can be trusted, because our words have weight.