Nedarim, Chapter Two, Mishnah Three
This mishnah continues to draw distinctions between vows and oaths.
1) There is a vow within a vow, but not an oath within an oath.
2) How is this so?
a) If one declares, Behold, I will be a nazir if I eat [this thing]; Behold, I will be a nazir if I eat [this thing] and then he eats [it], he is liable for each and every one.
b) I swear that I will not eat [this thing], I swear that I will not eat [this thing] and then he eats [it], he is only liable for one oath.
Section one: This section teaches that there is an additional stringency in vows that does not exist for oaths. One can make two vows on the same thing but not two oaths. The mishnah will now explain how this can happen.
Section two: If a person said twice that he will be a nazir if he eats a certain thing, and then he eats that thing, he must be a nazir twice. Since an unspecified nazirite period is thirty days (we will learn more about this in the next tractate), this person must act as a nazir for sixty days.
However, if he takes two oaths that he will not eat a certain thing, and then eats it, he is only liable for breaking one oath. If he breaks the oath intentionally he only receives one set of lashes, and if accidentally, he only brings one sacrifice.