Shevuot 20: Defining an Oath; False & Vain Oaths

The rabbis discuss oaths regarding eating.  To understand "I will eat", "I will not eat" and other oaths, the rabbis imagine scenarios.  For example, a person might refuse to eat after being pressured to eat.  The rabbis consider the possibility of an error in the text.

The rabbis wonder what is included in the definition of a shevua, an oath.  When something is not actually an oath, the person who makes that statement is not liable to punishment if s/he goes against those words.  An issar, for example could be understood as a vow said without vowing. A mitva is an obligation.  A neder is thought of as a binding agreement that is neither a vow nor an oath.  

These subtle differences in the understandings of verbal agreements reflects a society that took one's word with great seriousness.   Some rabbis argue that some of these binding agreements are subcategories of oaths and thus should be punished as oaths.

We learn about false oaths and vain oaths.  The rabbis argue about whether these two types of oaths might actually describe the same thing.  When a person swears or yells that s/he will not eat and then s/he eats, this is false and it is in vain.  It is false because the oath was not kept.  It is a vain oath because the oath was transgressed.  The rabbis teach that these two types of oaths were taught together.  Further, they were punished in the same way - with lashes.