Shevuot 29: Who Makes Oaths in Vain

We are introduced to a new Mishna.  It teaches us which can be categorized as oaths said in vain:

• An oath that goes against what is known to be true; for example "this (stone) pillar is made of gold", or "this is a woman" (when all know that this is a man)
• An oath is made about something impossible; for example "if I do not see a camel fly through the air" or "if I do not see a snake the size of the beam in an olive press"
• Witnesses who were asked to testify swore that they would not meet their obligation to testify
• A person swore not to fulfil another mitzvah; for example, not to dwell in a sukkah, take lulav, don tefillin, etc.

A person who makes an oath in vain is lashed.  If a person swears that s/he will eat a loaf and then swears that s/he will not eat it, s/he has transgressed regardless of what s/he does.  If s/he eats the loaf or does not eat the loaf, s/he has transgressed by making an oath in vain.

The Gemara begins by defining what it means for "people to know" what the truth must be.  This is three people.  We are reminded that it is not an oath to say, "if I did not see a camel fly".  Instead one must word an oath in the positive.  And in either case, the oath is said in vain for it is impossible to fulfil.  The rabbis joke that a man might see a huge bird, name it "camel" and swear truthfully about seeing a camel.  One must be judged based on the words that one said and not one's intention.  The rabbis then consider cases where one's own knowledge is different from one's outward behaviour or speech.*

A second new Mishna teaches us more about oaths said in vain.  We are taught that vain oaths regarding oneself apply to both men and women, relatives and strangers, people who are qualified to testify and people who are not qualified to testify, inside of the beit din and outside of the beit din.  If one transgresses, s/he is either lashed or s/he brings an offering.  A person can put an oath on someone else if that someone answers, "amen" after the person has stated the oath.

The Gemara shows us that each of these statements is questioned by Rabbi Meir and others.  Only a man should take this oath, only strangers, witnesses that are qualified to testify, and those outside of a beit din.   These are argued along with the statement that one who says, "amen" has agreed to an oath as if s/he had made the oath him/herself.