GEMARA: It is stated in the mishna: This is a stringency of oaths vis-à-vis vows. The Gemara presumes that the mishna is referring to the distinction stated in previous mishnayot between saying: An offering that I will not eat of yours, and saying: An oath that I will not eat of yours. The Gemara asks: Should it be derived by inference that the statement: An offering that I will not eat of yours, is a valid vow by rabbinic law, and it is merely less stringent than the corresponding oath, which takes effect by Torah law? But doesn’t the mishna teach that it is permitted for him to eat, implying that the vow does not take effect at all?

The Gemara answers: This is taught with regard to the latter clause of the other section. As opposed to a vow that is taken with regard to a matter that does not have actual substance, which takes effect only by rabbinic law, as articulated in the mishna (14b) and Gemara (15a), the subsequent mishna (15b) teaches that if someone says: An oath that I will not sleep, or: That I will not speak, or: That I will not walk, this activity is forbidden to him. It is concerning this contrast that the mishna says: This is a stringency of oaths vis-à-vis vows.

§ It is stated in the mishna that there is a stringency of vows vis-à-vis oaths. How so? Whereas a vow can override a mitzva, an oath cannot. Rav Kahana teaches that Rav Giddel said that Rav said, and Rav Tavyumei teaches the same statement with a different attribution, i.e., Rav Giddel said that Shmuel said: From where is it derived that one cannot take an oath to transgress the mitzvot? The verse states: “He shall not profane his word” (Numbers 30:3). It is inferred that his word, i.e., the prohibition he accepted upon himself, he shall not profane. However, he may profane it for the desires of Heaven. If he took an oath to act against the will of God, the oath does not take effect.

The Gemara asks: What is different about a vow that enables it to override mitzvot? Granted, as it is written in the Torah: “When a man takes a vow to the Lord…he shall not profane his word” (Numbers 30:3), which indicates that even with regard to matters that pertain to the Lord, i.e., mitzvot, one shall not profane his word, as the vow takes effect. However, with regard to an oath it is also written in the same verse: “Or swears an oath” to God, “he shall not profane his word.”

Abaye said: The distinction is not between oaths and vows per se, but rather between the phraseology in each case. How so? This case, in which the prohibition overrides the mitzva, is referring to one who said: The benefit derived from a sukka is hereby forbidden to me. Since the vow renders the sukka a forbidden object, it takes effect and overrides the mitzva, as one may not be fed what is forbidden to him, even if it is forbidden only to him. By contrast, that case, in which the prohibition does not take effect, is referring to one who said: I hereby take an oath that I will not derive benefit from the sukka. The oath does not take effect, as one is not entitled to take an oath to abstain from an act that he is obligated to perform.

Rava said in objection to the explanation of Abaye: But were mitzvot given for the purpose of deriving benefit? The performance of mitzvot is not considered benefit. Why then would performance of the mitzva with the sukka be considered deriving benefit? Rather, Rava said a different explanation: This case is referring to one who said: Dwelling in a sukka is hereby prohibited to me, and that case is referring to one who said: I hereby take an oath that I will not dwell in a sukka.

§ The Gemara asks: And is the principle that one cannot take an oath to transgress the mitzvot derived from here, i.e., the above verse? It is derived from there, i.e., another verse, as it is taught in a baraita: One might have thought that if one takes an oath to nullify a mitzva and does not nullify it, one might have thought that he will be liable for violating an oath on a statement.