Study Shevuot folio 29A with parallel Hebrew-English text, traditional commentary, and modern study tools. Free access to Babylonian Talmud online.
and he unwittingly ate figs and set aside an offering for breaking the second oath, and afterward he unwittingly ate grapes alone, he is exempt from liability for breaking the first oath. The grapes are tantamount to a half-measure of his first oath, which was not to eat figs and grapes together, a
Mishnah: Which oath is an oath taken in vain, mentioned in the previous Mishnah (27b)? It is when one takes an oath to deny that which is known to people to be true, for example, one says about a stone column that it is made of gold, or about a man that he is a woman, or about a woman that she is
Another type of oath taken in vain is when one takes an oath about a matter that is impossible, e.g., if he says: If I did not see a camel flying through the air, or: If I did not see a snake as large as the beam of the olive press.
In the case of one who said to witnesses: Come and testify for me, and they replied: On our oath we will not testify for you, that is an oath taken in vain, because it involves taking an oath to refrain from performing a mitzva. Other examples of this include an oath not to build a sukka, or not
If one said: On my oath I will eat this loaf, and later said: On my oath I will not eat it, the first oath is an oath on an utterance, and the second is an oath taken in vain, as he took an oath to perform an action that would violate his previous oath.