Before you learn Bekhorot 46

Where we left off

Daf 45 concluded debating whether a vow taken in public can ever be dissolved. This sugya continues immediately at the top of daf 46.

When can a public vow be annulled, and what physical emergence halakhically defines a firstborn?

נדר על דעת רבים (vow made with public consent): A vow administered with public consent cannot ordinarily be dissolved by a Sage. However, an authority may dissolve it if nullification serves a mitzva.
בכור לנחלה (firstborn for inheritance): The double portion belongs to the biological first issue of the father. A prior non-viable fetus does not prevent a subsequent son from receiving this right.
פטר רחם (opener of the womb): Redemption from a kohen depends solely on opening the mother's womb. Even an unviable miscarriage can open the womb and exempt later brothers.
פדחת (forehead): The emergence of the forehead is halakhically treated as the emergence of most of the head. The Gemara debates whether seeing the forehead constitutes valid recognition for inheritance rights.

Ameimar (אמימר, Amora): He rules that a vow dependent on public consent is dissolvable only for a mitzva.
Shmuel (שמואל, Amora): He claims that the emergence of a head in a miscarriage does not constitute birth.
Rabbi Shimon ben Lakish (רבי שמעון בן לקיש, Amora): He holds that the emergence of a forehead constitutes birth everywhere except for inheritance.
Rabbi Yochanan (רבי יוחנן, Amora): He rules that the emergence of the forehead counts as birth even for inheritance.