Shevuot 26B

איזו היא שגגת שבועת ביטוי לשעבר? אי דידע ⁠– מזיד הוא! אי דלא ידע ⁠– אנוס הוא!

What is the case of an unwitting oath on an utterance referring to the past, for which one is liable to bring an offering? If it is a case where he knows when he takes the oath that it is not true, then he is an intentional taker of a false oath and may not bring an offering. If it is a case where he did not know at the time of taking the oath that what he was saying is not true, then he is a victim of circumstances beyond his control, and is exempt from bringing an offering.

אמר ליה, באומר: ״יודע אני ששבועה זו אסורה, אבל איני יודע אם חייבין עליה קרבן או לאו״.

Rav Naḥman said to him in answer to his question: It is a case where the one taking the oath says: I know that taking this oath is prohibited, but I do not know if one is liable to bring an offering for it or not. Since he does not know the full implications of his action, it is regarded as unwitting, and he may still bring an offering to atone for it.

כמאן ⁠– כמונבז, דאמר: שגגת קרבן שמה שגגה?

Rava asked Rav Naḥman further: In accordance with whose opinion do you answer in this way? Is it in accordance with the opinion of Munbaz, who says: Lack of intention with regard to the offering, i.e., ignorance as to whether one’s action renders one liable to bring an offering, is regarded as lack of intention? There is a dispute between Munbaz and the Rabbis in tractate Shabbat (69a–b) with regard to one who knows that a particular action desecrates Shabbat but does not know that it renders one liable to bring a sin-offering. Munbaz holds that even one who is merely ignorant of the liability to bring an offering is deemed an unwitting sinner who brings a sin-offering to atone. The Rabbis disagree and deem him unwitting only if he is unaware that the action is prohibited.