(Mishnah): If a (childless) man went overseas with a wife and left a wife (Leah) home and they told Leah that he died, she may not remarry nor do Yibum until she hears whether or not she, her Tzarah, is pregnant;

If Leah has no Yavam but has a mother-in-law overseas, she need not be concerned lest a Yavam was born;

If her mother-in-law was pregnant and went overseas, Leah must be concerned lest a Yavam was born (she may not remarry);

R. Yehoshua says, she need not be concerned.

(Gemara) Question: Why does it say 'she, her Tzarah'? (This is unnecessary!)

Answer: We are concerned only for a Tzarah we know about. We are not concerned lest he married a woman overseas.

(Mishnah): She may not remarry nor do Yibum ...

Question: Granted, she may not do Yibum. If her Tzarah is pregnant, the Yavam is forbidden mid'Oraisa due to Eshes Ach without the Mitzvah of Yibum.

However, why can't she remarry? We should assume that the Tzarah is from the majority of women who get pregnant and have children!

Answer #1: The Mishnah is R. Meir, who is concerned for the minority.

Answer #2: The Mishnah can even be as Chachamim;

Chachamim follow a Ruba d'Isa Kaman (a majority in front of us that we can count it), e.g. if there are nine stores (in this city that sell Kosher meat and one sells Tereifah, and meat was found and we do not know from which store it came);

Also regarding Beis Din (we follow the majority of judges);

We do not find that Chachamim follow a Ruba d'Leisa Kaman (i.e. a statistical majority, e.g. most women get pregnant and have children).

Objection: When a minor falls to Yibum, Chachamim rely on a Ruba d'Leisa Kaman!

(Beraisa - R. Meir): A minor Yavam or Yevamah does not do Chalitzah or Yibum;

Chachamim: We understand why they cannot do Chalitzah. "Ish" must be an adult, and we equate the law of the Yevamah to the Yavam;

Question (Chachamim): Why can't they do Yibum?

Answer (R. Meir): If he is a minor, we are concerned lest he be found to be a Seris. If she is a minor, we are concerned lest she is an Ailonis. In either case (there was no Mitzvah of Yibum, so) they transgressed Ervah.

Chachamim rely on the majority. Most people are normal males and females.

Conclusion: We must say that our Mishnah is R. Meir.

Objection (Seifa): If she has no Yavam but has a mother-in-law overseas, she need not be concerned lest a Yavam was born.

If the Mishnah is R. Meir, we should be concerned!

Most women get pregnant and bear children. A minority miscarry. Of those who bear children, half are male;

The chance that her mother-in-law bore a son is less than half. R. Meir is concerned for a minority!

Answer: Since Leah's Chazakah is that she will not fall to Yibum when her husband dies, R. Meir is not concerned for the minority.

Objection: If so, in the Reisha her Chazakah is that she will fall to Yibum. She should do Yibum!

Answer #1 (Rav Nachman): There, to do Yibum is Chayavei Kerisos (if indeed he had a son and Yibum does not apply), so we are concerned. Yevamah l'Shuk (if there is a Yavam) is only Chayavei Lavin, so we are not stringent.

Rejection (Rava): Both are mid'Oraisa. We should be as stringent about Chayavei Lavin as we are about Chayavei Kerisos!

Answer #2 (Rava): In the Reisha, her Chazakah is that she will fall to Yibum, and the majority says that she will not. A Chazakah is not as strong as a majority, so it joins with the minority of women who miscarry, and we are left with an even doubt, so she may not do Yibum or marry l'Shuk;

In the Seifa, the Chazakah and the majority both say that she will not fall to Yibum. Therefore, the chance that a Yavam was born is considered miniscule, and even R. Meir is not concerned for this.

(Mishnah): Leah may not marry l'Shuk or do Yibum ...

Question: Can she never remarry?

Answer #1 (Ze'iri): She must wait three months to see if she herself is pregnant. She must wait nine months lest her Tzarah is pregnant. After this Leah does Chalitzah, and she is permitted l'Shuk whether or not her Tzarah bore a child.

Answer #2 (R. Chanina): She must wait three months to see if she herself is pregnant. She must wait forever for her Tzarah (i.e. until witnesses say whether or not she gave birth)!

Question: Why can't Leah do Chalitzah after nine months, whether or not her Tzarah had a child?

Answer (Abaye bar Avin and R. Chanina bar Avin): This is a decree, lest the Tzarah had a child, and we will have to announce that the Chalitzah was unnecessary and void, so Leah is permitted to a Kohen.

Question: What is wrong if we need to announce this?!

Answer: Perhaps someone who saw the Chalitzah will not hear the announcement. When he sees her marry a Kohen, he will think that a Chalutzah was permitted to a Kohen.

(Mishnah): If a woman says 'I had a son overseas. My son died, and then my husband', she is believed. If she says 'My husband died, and then my son', she is not believed, and we are concerned for her words. She does Chalitzah, not Yibum.

Question: We should be concerned lest witnesses come and verify her story, and we will have to announce that she is permitted to a Kohen!

Answer #1 (Rav Papa): That Mishnah discusses a divorcee.

Answer #2 (R. Chiya brei d'Rav Huna): The case is, she said that she and her husband were alone in a cave. We are not concerned lest witnesses come.

Note: Perhaps she knows the Halachah, and falsely says that they were alone, so we will permit her to do Chalitzah. Later, witnesses will come and verify her story, and she will be permitted to a Kohen! Perhaps she disqualified such witnesses from testifying for her, for according to her, they lie. Indeed, if she disqualifies herself to Kehunah in any way, she may do Chalitzah. The Me'iri connotes like this.

(Mishnah): Sarah and Leah were married to two brothers. Each said 'My husband died (without children)'. Leah cannot remarry, lest Sarah's husband (her Yavam) is alive. Likewise, Sarah cannot remarry.

If Sarah has witnesses that her husband died, and Leah has no witnesses that her husband died, Sarah may not remarry, but Leah may;

If one man died with children and the other without children, the widow with children may marry. The other widow may not;

If Sarah and Leah did Yibum (to other brothers), and the Yevamim died, the women may not remarry;

R. Elazar says, since they were permitted to the Yevamim, they are permitted to others.

(Gemara - Beraisa): If Sarah has witnesses and children, and Leah has neither, both may remarry;

If (neither had witnesses or children and) they did Yibum and the Yevamim died, they are forbidden;

R. Elazar says, since they were permitted to the Yevamim, they are permitted to others.