Nedarim, Chapter Two, Mishnah One
The first section of this mishnah deals with vows that are not binding. The second and third sections deal with vow that are semi-binding.
1) And these [vows] are not binding:
a) [One who says] What I eat of yours shall be unconsecrated; As the flesh of the swine; As an object of idolatrous worship; As hides pierced at the heart; As carrion; As terefoth; As abominations; As creeping things; As Aarons dough; As his terumah–[in all these cases the vow is] not binding.
2) If one says to his wife, Behold! You are like my mother to me, he must be given an opening on other grounds, in order that he should not act lightly in such matters.
3) [If one says,] Konam if I sleep; If I speak; or If I walk; or if one says to his wife, Konam if I cohabit with you, he is liable to [the biblical prohibition] he shall not break his word (Numbers 30:3).
4) [If he says,] I swear] an oath not to sleep, or, talk, or, walk, he is forbidden [to do so].
Section one: I shall explain each of these cases one at time.
What I might eat of yours shall be unconsecrated: Unconsecrated food is permitted, hence he has not stated that anything should be prohibited to him.
As the flesh of the swine: Vow formulas only work if the object used as a vow is something which can be vowed/dedicated to the Temple, such as an offering. While swine and the subsequent objects listed in this mishnah are forbidden, they cannot be offered to the Temple, and hence the vow is invalid.
As an object of idolatrous worship: This vow does not work for the same reason as above.
As hides pierced at the heart: These were used in idol worship.
As carrion; As terefoth; As abominations; As creeping things: These are all things which Jews may not eat. Carrion is an animal which was slaughtered improperly, terefoth are animals which died or would have died without being slaughtered. Abominations and creeping things are forbidden reptiles and other small animals, all of which are forbidden to eat. Again, the vow formula is ineffective because he didnt vow using something which can be donated to the Temple.
As Aarons dough; As his terumah: These are both gifts that must be given to priests (Aarons sons). They are forbidden for consumption for non-priestly Jews. However, since one cannot offer them to the Temple, they cannot be used in vow formulas.
Section two: In this case, a husband attempts to forbid his wife to himself sexually, by stating that she should be to him like his mother, who is obviously prohibited to him (nothing Oedipal here). The vow does not work, since he didnt use something that can be vowed as part of his vow formula. However, the rabbis did not want people to take these matters lightly and hence they said that he had to find an opening for breaking his vow. For this, he will need to see a Sage. We will learn more about how this is done towards the end of the tractate.
Section three: At the end of the previous chapter we learned that a vow does not work on something that has no substance. Therefore, when one says Konam (a valid formula) that I should not do something the vow is not valid, since actions do not have substance. However, our mishnah rules that the one who took such a vow should nevertheless keep his word. He still must follow the prohibition in Numbers 30:3, that a person must do all that he promised.
In contrast, oaths (shevuoth) can be made on actions, for an oath relates to the person and not to the object. Therefore, one who swears an oath not to do something is bound by Torah law to keep his word.