How does annulment affect hatpasah? TB Nazir 21

If you remember, we learned about the concept of hatpasah (התפסה) in massekhet Nedarim. Hatpasah is a method of declaring an object prohibited by “latching it onto” (i.e. comparing it to a previous prohibited item). The first Mishna of the fourth chapter of our massekhet found on yesterday’s daf TB Nazir 20b is clear about the outcome in two scenarios, but unclear in a third scenario. Today’s daf TB Nazir 21 thoroughly examines the third scenario.

Here is the case study of hatpasah in nezirut. The first person says, “I’m hereby a nazir,” and a second person latches on by saying, “me too,” and a third person also latches on by, “me too.” The Mishna describes the outcome when the first person or the last person has his vow annulled. “If the vow of the first was dissolved by a halakhic authority, they are all dissolved. However, if the vow of the last individual was dissolved by a halakhic authority, the vow of the last individual alone is dissolved, and all the others remain bound by their nazirite vows.” (Sefaria.org translation) When the middle person as his vow of nezirut annulled, is the third person in the chain’s vow to become a nazir become annulled because he attached his vow to the middle person? Or alternately, does the third person remain a nazir because he attached his vow to the first person?

The Gemara brings four tannaitic sources to answer this question. It rejects the first three sources as inconclusive because they could be interpreted either way. Only with the fourth source is our question conclusively answered. “Come and hear, as it is taught in a baraita explicitly: If the first one is dissolved, they are all dissolved; if the last one is dissolved, the last one is dissolved and they are all bound by their vows. If the middle one is dissolved, the vows of anyone from him and after him are dissolved; those who vowed from him and before him are bound by their vows. One can learn from this that each associates himself with the vow of the other individual. The Gemara concludes: Learn from this that it is so” (Sefaria.org translation) In fact this is the halakha. (Rambam, Mishneh Torah, Book of Oaths, Laws of Vows, chapter 4, halakha 9; Shulkhan Arukh, Yoreh De’ah 229:3)

Why didn’t the Gemara bring the fourth source and answer the question immediately instead of providing three rejected sources? I can suggest three possible answers. First of all, this source may not have been known during the discussion. Only when the Gemara was being redacted did the editor bring the source to the table. Alternatively, this anonymous source could have been an opinion of only one individual that ultimately was accepted as the halakha. The explanation I like best is the bet midrash, the academy, wanted a thorough examination and discussion of the Mishnah before coming to the conclusion. Although I never went to law school, I imagine this is the type of discussion that goes on to train the students’ minds in legal theory. The professors don’t necessarily teach the bottom line of what the law is. That the students can always look up.