What is an invalid oath? [For example:] He swore to a statement contrary to common knowledge; he said of a stone pillar that it was gold; that a man was a woman, or that a woman was a man. If he swore regarding an impossible condition, for example, [I swear] that I have seen a camel flying in the air, or that I saw a snake as thick as an olive-press beam. If one asks witnesses to come testify for him and they swear that they will not testify [as required by law]. Or if he swore to annul the commandments: not to make a sukkah, not to take the lulav, not to wear tefillin—these are all instances of an invalid oath. For these, one who violates intentionally is punished with lashes, but one who violates unintentionally is exempt [from punishment].
The mishnah is very concerned with oath taking, especially when the people offering oaths are not careful about their claims. This mishnah catalogues vain or invalid oaths. In all cases, the apparent sincerity of the oath is undermined by the absurdity of the statement.