[If] one swore to annul a mitzvah, and did not annul it —- he is exempt; to fulfill [a mitzvah], and he did not fulfill [it] —- he is exempt. For it might have been inferred that he be liable, as is the opinion of R' Yehudah ben Beseira. Said R' Yehudah ben Beseira: If for an optional matter, concerning which he was not adjured from Mount Sinai, he is liable; [then] for a mitzvah, concerning which he is adjured from Mount Sinai, is it not certain that he should be liable? They said to him: No! If you say this as regards an optional oath, it is because [Scripture] has made negative equal to positive in that regard. Will you say this in the case of an oath to fulfill a mitzvah, in which [Scripture] did not make negative equal to positive? For if he swears to annul it and does not annul it, he is exempt.

“I swear that I will not eat this loaf”; “I swear that I will not eat it”; “I swear that I will not eat it,” and he ate it —- he is liable only once. This is the oath of utterance for which one is liable for its willful transgression to [a penalty of] lashes, and for its inadvertent transgression to a variable [sin-] offering. [For] a vain oath —- one is liable for its willful transgression to [a penalty of] lashes, and for its inadvertent transgression, one is exempt.

What is a vain oath? One [who] swears to contradict what is known to man: [For example,] he said concerning a pillar of stone that it is of gold, concerning a man that he is a woman, or concerning a woman that she is a man. One [who] swears concerning some-thing that is impossible: [for example,] “If I did not see a camel flying through the air,” or, “If I did not see a snake like the beam of an olive press.” One [who] said to witnesses, “Come and testify for me,” [and they replied,] “We swear that we will not testify for you.” One [who] swears to annul a mitzvah; [for example,] not to make a succah, not to take a lulav, or not to put on tefillin. These are the vain oaths for which one is liable to [a penalty of] lashes for their willful transgression, and for whose inadvertent transgression one is exempt.

“I swear that I will eat this loaf,” “I swear that I will not eat it” —- the first is an oath of utterance, and the second is a vain oath. [If] he eats it —- he transgresses [only the prohibition against] a vain oath; [if] he does not eat it —- he transgresses an oath of utterance [as well].