Rabba and Rava, two amoraim, reframe the entire disagreement TB Nedarim 25b-26

Today’s daf TB Nedarim 26 is difficult and complex and I shall try to summarize the basic difference between Rabba and Rava. This disagreement actually begins on yesterday’s daf. We have a disagreement between Beit Hillel and Beit Shammai concerning a vow that only one clause of the vow is mistaken. “One who saw people entering his courtyard and eating figs, and because he did not want them to do so he said: The figs are forbidden to you like an offering. And then it was found that his father and brother were in the group, and there were others with them as well, and certainly he did not intend to take a vow prohibiting his father and brother from eating the figs. In such a case, Beit Shammai says: They, his father and brother, are permitted to eat the figs, and those others that were with them are prohibited from doing so. And Beit Hillel says: Both these and those are permitted to eat the figs, as will be clarified in the Gemara.” (Sefaria.org translation) Based on another Mishna we learned that Rabbi Akiva taught the underpinning reason of Beit Hillel. “A vow that was partially dissolved is dissolved completely.” (Sefaria.org translation) Beit Hillel, Beit Shammai, and Rabbi Akiva are all tannaim.

Rabba and Rava, two amoraim, reframe the entire disagreement when we apply the rule “A vow that was partially dissolved is dissolved completely.”

“Rabba said: Everyone in the mishna, i.e., Beit Shammai and Beit Hillel, holds that wherever one says: Had I known that my father was among you I would have said: All of you are prohibited from eating figs except for father, then in that case all are prohibited from doing so and his father is permitted to do so. They disagreed only in an instance where one said: Had I known that my father was among you then I would have said: So-and-so and so-and-so, i.e., all the others, are prohibited from eating figs and father is permitted to do so.” (Sefaria.org translation) There are two aspects to the vow, the intent and the language of the vow. Rabba holds that Beit Hillel would only apply the rule “A vow that was partially dissolved is dissolved completely” when both aspects of the vow, the intention and the language of the vow, are wrong. In the above case the person making vow says “Had I known my father was amongst you” shows a mistaken intent and when he says “I would have said So-and-so and so-and-so” shows that the original language was wrong.

“And Rava said: Everyone holds that anywhere that one says: Had I known that father was among you I would have said: So-and-so and so-and-so are prohibited to partake and father is permitted to do so, then all are permitted to partake. They disagree only in a case where one says: Had I known that father was among you I would have said: All of you are prohibited from partaking except for father.

“The rationale of the dispute is the following: Beit Shammai hold in accordance with the opinion of Rabbi Meir, who said: If one initially makes one declaration and immediately afterward makes a conflicting declaration, hold him accountable for the first expression. Since he initially said: All of you are prohibited from partaking, this expression is the effective one and they are all prohibited from doing so. The addition of the words: Except for father, is viewed as a clarification of the previous expression, simply indicating that his father is not included in the prohibition. (Rabbi Meir looks at the intent of the first statement. Since you are only adding an addendum, you’re just clarifying the intent of the first statement. The intent hasn’t changed. Consequently, Beit Shammai would hold that everybody except the father is still prohibited from eating the figs.-gg)

“And by contrast, Beit Hillel hold in accordance with the opinion of Rabbi Yosei, who said: A person is held accountable even for the conclusion of his statement, and the second formulation is the primary one. Therefore, the fact that one altered his formulation to exclude his father from the prohibition means that the vow is partially canceled, and a vow that is partially dissolved is dissolved completely. (The only time Beit Hillel would apply the rule “A vow that was partially dissolved is dissolved completely” is when the vow’s language is redacted with an addendum. This addendum creates a brand new vow and now the rule is applied.-gg)” (Sefaria.org translation)

The disagreement between Rabbi Meir and Rabbi Yosei originates TB Temurah 25b