Talmud - Nedarim 15b נדרים ט״ו ב׳

And this is a conclusive refutation of the opinion of Rav Yehuda.

The Gemara answers: When the mishna teaches this, it does not mean that before she went she was permitted to derive benefit from him ab initio. Rather, it means that if she derived benefit from him after the fact, she is in violation of: He shall not profane his word.

We learn further on (57b) that if the husband said to his wife: Deriving benefit from me until the festival of Sukkot is konam for you if you go to your father’s house until Passover, then, if she went before Passover, she is prohibited from deriving benefit from him until the festival of Sukkot, as the vow took effect, and she is permitted to go to her father’s house after Passover.

The Gemara infers: Only if she went before Passover is it prohibited for her to derive benefit from him. However, if she did not go it is not prohibited for her to do so. She may derive benefit from him, and there is no concern that she will subsequently go to her father’s house, transgressing the prohibition. This is difficult according to the opinion of Rav Yehuda that one may not perform an action that will be rendered retroactively a violation of a vow if the condition is met.

Rava said: The same is true, that even if she did not go, she is prohibited from deriving benefit from him. The difference is that if she went it is not only prohibited for her to derive benefit from him, but if she does so she is flogged; whereas if she did not go, it is merely prohibited for her to derive benefit from him, lest she violate the vow by going to her father’s house before Passover.

The Gemara raises an objection to the opinion of Rav Yehuda: It is taught in a baraita that if one said: This loaf is forbidden to me today if I go to such and such a place tomorrow, then if he ate the loaf today, he is subject to the prohibition that he shall not go tomorrow. Apparently, he may eat it today, as there is no concern that he will go tomorrow.

The Gemara answers: Where is the contradiction? Does the baraita teach that he may eat the loaf ab initio? It teaches only that he ate, i.e., that once he ate, he is subject to the prohibition that he shall not go.

It is further taught in the baraita: If he went the next day, he is in violation of: He shall not profane his word. The Gemara infers from the fact that the baraita is referring only to a case in which he went after the fact, that he may not go ab initio. This indicates that he is permitted to eat the loaf, thereby prohibiting himself from going the next day. This accords with the opinion of Rav Naḥman that one may cause a vow to take effect by fulfilling its condition, and it poses a difficulty to the opinion of Rav Yehuda.

The Gemara answers: Rav Yehuda could have said to you that the same is true, that the baraita could have taught that he may go. However, since the first clause teaches the halakha where he ate the loaf after the fact, as it cannot teach that he may eat it according to Rav Yehuda, who holds that it is prohibited for him to eat it ab initio, the latter clause also teaches the halakha in the case where he went, and does not teach that he may go, to maintain a uniform style. In conclusion, neither opinion is refuted.

§ It is taught in the mishna that with regard to one who says to his wife: Engaging in sexual intercourse with you is konam for me, if he violates the vow he is in violation of the prohibition: He shall not profane his word. The Gemara asks: How can one render prohibited engaging in sexual intercourse with his wife? But isn’t he duty bound by Torah law to engage in sexual intercourse with her, as it is written: “Her food, her clothing, and her conjugal rights he may not diminish” (Exodus 21:10)?

The Gemara answers: The vow does not take effect if it is formulated as cited. Rather, the mishna is referring to a case where he says: The pleasure I derive from engaging in sexual intercourse with you is forbidden to me, and sexual intercourse is therefore not amenable to him. Since he is not obligated to experience the pleasure he derives from sexual intercourse with her, he can prohibit himself from experiencing this pleasure. In this manner he can render their sexual intercourse forbidden by means of a vow.

As Rav Kahana said: If a woman vows: Sexual intercourse with me is forbidden to you, the court coerces her to engage in sexual intercourse with him, as she is duty bound to engage in sexual intercourse with him due to his conjugal rights. However, if she vows: The pleasure I derive from engaging in sexual intercourse with you is forbidden to me, it is prohibited for them to engage in sexual intercourse, as she derives pleasure from the sexual intercourse and one may not feed a person that which is forbidden to him.

MISHNA: If one says: I take an oath that I will not sleep, or: That I will not speak, or: That I will not walk, this activity is prohibited to him. As taught earlier (10a), one of the primary methods of taking a vow is by invoking an offering. The mishna provides several examples where invoking the term korban is not effective. If one says: An offering [korban] that I will not eat of yours, or: This offering [ha korban] that I will eat of yours, or: That which I will not eat of yours is not an offering [la korban], the food is permitted.

Traduction : The William Davidson digital edition of the Koren Noé Talmud, with commentary by Rabbi Adin Even-Israel Steinsaltz.

Nedarim 15b examines conditional vow violations, debating whether Rav Yehuda permits acting before a future condition retroactively breaches an oath.