If one makes a neder or shevu'ah to do something that is forbidden by Torah (or perhaps to abstain from something that is mandatory) what happens?

  1. Does his vow have any significance? That is, was it an actual vow?

  2. Was making such a vow a sin? If "no" to question #1, then why?

  3. Must he/can he annul the vow? (If "no" to #1, why?) Are there any special procedures for doing so in such a case?

  4. What obligations rest on him after making the vow, and before annuling it? What would be his proper course of action if the situation he vowed about presented itself...?

  • 2
    There is a concept in the Gemara in nedarim, that one who makes a shvuah to fulfill a mitzvah it wouldn't be valid, as we are already obligated to keep the mitzvah (the Gemara says in the end it is valid for the purpose of giving oneself extra motivation). Seemingly this would apply as well to aveiros. מושבע ועומד בהר סיני Commented May 24, 2017 at 6:47
  • 2
    Making such a vow is a sin if you used a divine name as that would be using it in vain. The vow would not be valid.
    – CashCow
    Commented May 24, 2017 at 10:27
  • Shvu'at shav -- jewishpress.com/judaism/halacha-hashkafa/… 3rd paragraph -- not an answer b/c it lacks any citations though I assume Ketuot 70
    – rosends
    Commented May 24, 2017 at 10:49
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    One who swears that contradicts an already sworn oath is invalid. All of us already swore to obey the Torah at Sinai. Commented May 24, 2017 at 11:29
  • In the title you say swear but in the body you say vow. Neder and Shevua are different things with different rules.
    – Double AA
    Commented May 24, 2017 at 14:27

2 Answers 2


As we see in a number of places, an oath to transgress a mitzvah is invalid from the beginning because it contradicts the oath taken at Sinai to observe hashem's commandments. Rambam and others state that there is a difference between an oath (shvua) and a neder. An oath does not cancel the oath he took at Sinai as it applies to the person. A neder applies to the object and he is forced to have the neder annulled.

One should also note the difference between a neder to not use a particular succah and one to refrain from using any succah

OUTLINES OF HALACHOS FROM THE DAF NEDARIM 16 is too long to copy all of it but here are a few points.

1.(Mishnah): A stringency of Nedarim over Shevuos is that if one said 'Konam Sukah, I will not make one' or similarly regarding Lulav, or Tefilin, he is forbidden. Such a Shevuah does not forbid, for one cannot swear to override Mitzvos.

2.(Rav Gidal): "Lo Yachel Devaro." - one may not profane his own word, but he may for the sake of Hash-m's word (an oath to transgress a Mitzvah is void).

Rambam (Hilchos Nedarim 3:6): A Neder is Chal (takes effect) on Mitzvos like on Reshus (optional matters). (Note not a shevuah)

  • Radvaz: A Neder is Chal to desist from a Mitzvah of action. A Neder to eat pork is not Chal. We do not say that the Aseh "Motzei Sefasecha Tishmor" overrides a Lav, for he brought the Aseh upon himself.

Shulchan Aruch (YD 215:1): A Neder is Chal on Mitzvos. If one said 'Konam Sukah, I will not sit (in one), a Lulav, I will not take one', he may not sit in a Sukah or take a Lulav.

Rema: Some say that we lash him for vowing to Mevatel a Mitzvah, and permit it, and he fulfills the Mitzvah. Some say that there are no lashes for a vain vow, only for a vain oath.

Shulchan Aruch (5): A Neder is Chal on a Mitzvah only regarding an Aseh, whether or not there is a Lav for being Mevatel it.

Shulchan Aruch (6): Some say that the Neder is Chal. If he eats it, he transgresses "Lo Yachel." However, if he was Matfis something else in it, it is not forbidden, for he intends for the initial Isur, which is Davar ha'Asur. However, if something is forbidden mid'Rabanan and he forbade it through a Neder and was Matfis something else in it, it is forbidden.

Rambam Nedarim 3:6-7

6 What is meant by the statement that vows take effect with regard to mitzvot as well as actions that are left to one's choice? When a person says: "Matzah is forbidden to me on Pesach night," "Dwelling in a sukkah on that holiday is forbidden to me," or "I am forbidden to take hold of tefillin," they are forbidden to him. If he ate matzah, dwelled in a sukkah, or took tefillin, he is liable for lashes.11 Similar laws apply in all analogous situations. Needless to say, one who says: "I am obligated to bring a sacrifice if I eat matzah on Pesach night," is obligated to bring a sacrifice.12 Similar laws apply in all analogous situations.

11. For breaking his vow. The Rama (Yoreh De'ah 215:1) mentions a view that maintains that the person should be given corporal punishment for taking such a vow and should be compelled to ask to have the vow released.

12. For he can fulfill the mitzvah and bring the sacrifice (the Rambam's Commentary to the Mishnah, Nedarim 2:2).

7 Why do vows take effect with regard to mitzvot and oaths do not take effect with regard to mitzvot? Because when a person takes an oath he forbids himself from [partaking of] the entity mentioned in the oath.13 When, by contrast, one takes a vow, he causes the entity mentioned in the vow to be forbidden to him.14 Thus when a person takes an oath to nullify a mitzvah, he is placing a prohibition upon himself and he is already bound by an oath [to observe that mitzvah] from Mount Sinai, and one oath does not take effect if another is already in effect. When, by contrast, a person causes an entity to be forbidden through a vow, the prohibition involves the entity itself and that entity is not under oath from Mount Sinai.

13. I.e., the prohibition involves the gavra, the person himself. It cannot take effect if he is already bound to act otherwise.

14. I.e., the prohibition involves the cheftzah, the article. Once it is forbidden, it is forbidden to fulfill the mitzvah by partaking of it or using it, for a positive commandment does not supercede a negative commandment. It would be a mitzvah fulfilled through a transgression which is a forbidden act (the Rambam's Commentary to the Mishnah, loc. cit.).


The Mishna in Nedarim (16a) states,

אמר קונם סוכה שאני עושה לולב שאני נוטל תפילין שאני מניח בנדרים אסור בשבועות מותר שאין נשבעין לעבור על המצות:

This means that if someone makes a neder to annul a Mitzvah (in your words to abstain from something mandatory) it works, and he cannot do the Mitzvah until he annuls his neder. On the other hand, if he makes a Shvua to annul a Mitzvah it doesn't do anything since he is already "מושבע ועומד מהר סיני"; which means that since he has already accepted the vow at Sinai to do them, his shvua is null and void. The reason why the neder works in this case is because a neder is a "איסור חפצא" which means that it (the sacredness of the pledge) rests on the object not on the person, and since the object can become ussur to him he cannot do it.

However, the Rambam (shvuos 5:18) states that in certain cases even a shvua can work to annul a Mitzvah, that is if he makes a general vow not to eat Matzah for a few years, he cannot eat Matzah even on Pesach. the reason why it is so is because "מתוך שחלה שבועה על שאר הימים חלה על ליל הפסח".

In the case when the shvua was null and void (mentioned above) the Rambam states that he gets "malkos", since he made a "שבועת שוא" which means a "useless vow" that is explicitly forbidden to make (ibid 5:14). If this punishment applies by nedorim, see Rema and Shach beginning of siman 215 YD. Regardless of whether he gets malkos, everyone seems to agree that it is ussur to do.

One more point: since nedarim are always negative (i will not do so and so) your first question is not sensible (If one makes a neder... to do something that is forbidden by Torah), since you can never make a neder to do something. Regarding a shvuah in such a case (i will do something forbidden) the previous din would apply in this case as well, and the shvuah would be null and void.

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