Please answer the following questions:
1. What is Bais Hillel's reasoning for saying that an ervah causes her tzarros to be exempt from chalitzah and yibum?
2. Why is a tzarrah exempt altogether from chalitzah and yibum if one of the wives does yibum?
3. Does Bais Shammai disagree with the principle that if one wife does yibum, the tzarros are exempt, or does he disagree that an ervah exempts her tzarros? Why? ( I think that there are two answers given by the Gemarah in Yevamos, daf 13, amud 2, to this question, one given by Rav Shimon ben Pazi and the other given by Rava.)
1. The Gemara cites two Pesukim for the Petur of a Tzarah: "Aleha" on 3b, and "v'Lakchah" on 8b.
2. Because of the principle "Bayis Echad Hu Boneh v'Eino Boneh Shnei Batim," and the principle "Kol she'Oleh l'Yibum Oleh l'Chalitzah" (41a).
3. Bais Shammai agrees.
Dov Zupnik