(Mishnah): Reuven and Shimon were married to Rachel and Leah (sisters); Levi (another brother) was single. Reuven died, Levi gave a Ma'amar to Rachel, and then Shimon died;

Beis Shamai say, Levi keeps his wife (Rachel). Leah is Achos Ishto (she does not need even Chalitzah);

Beis Hillel say, he sends his wife away with a Get and Chalitzah, and does Chalitzah to Leah.

About this case, they said 'woe to him! He loses his wife and his brother's wife.'

(Gemara): Beis Shamai hold like R. Elazar ben Arach, for R. Elazar ben Arach says that a Ma'amar makes a full Kinyan in a Yevamah.

Objection: If they hold like R. Elazar ben Arach, if he divorced Ba'alas ha'Ma'amar, she should not need Chalitzah;

(R. Heila citing R. Lazar): Beis Shamai agree that if he divorced Ba'alas ha'Ma'amar, she needs Chalitzah!

Retraction: Rather, [Beis Shamai] hold like R. Shimon, who says that [it is a Safek whether] Ma'amar acquires or does not acquire.

Question: If they hold like R. Shimon, no matter what you will say, [it is difficult]!

If Ma'amar acquired, there is no [Zikah] after it. (Why do they require Chalitzah after the Get?)

[If you will say that Chalitzah is because perhaps] Ma'amar did not acquire, why did it teach 'he keeps his wife, and the other goes out (is permitted automatically) due to Achos Ishto'? (If it did not acquire, his 'wife' is Achos Zekukaso! We explained this like PNEI MOSHE.)

Answer: Perhaps Ma'amar according to Beis Shamai is like Zikah according to R. Shimon, according to Rabanan there (in Bavel)'

Just like Rabanan say that Ma'amar acquires [partially] and leaves over, so R. Shimon says that Zikah acquires [partially] and leaves over;

R. Shimon says that Zikah does not take effect where there is already Zikah [from the first sister, i.e. even on the remnant that the first Zikah did not acquire]. So Beis Shamai say that Zikah does not take effect where there is a Ma'amar [i.e. on the remnant that the Ma'amar did not acquire].

Question (R. Yudan): If one was Mekadesh a woman from now and after 30 days (this is like partial Kidushin, like a Ma'amar), and her sister fell to him [for Yibum] within 30 days, [do Beis Shamai say that] even in such a case, he keeps his wife, and the other goes out due to Achos Ishto?

Answer: Beis Shamai said [that the latter sister is exempt] only when there was Zikah and Ma'amar [of the first sister].

[If not,] what R. Avahu said citing R. Yochanan, that [if one was Mekadesh a woman from now and after 30 days, and another was Mekadesh her from now and after 29 days...] even Kidushin of 100 [men] can take effect in her, will you say that it is unlike Beis Shamai?! (We explained this like RIDVAZ.)