1) SUMMARY: HOW A SHOMERES YAVAM BECOMES A SOTAH
The Gemara cites proof from the Mishnah in Sotah for Rav's opinion that "Yesh Chupah l'Pesulos" -- the Chupah which a Kohen performs with a Bas Kohen who is not permitted to marry a Kohen (such as a divorcee) is considered a valid Chupah and terminates her rights to eat Terumah (see previous Insight). The Mishnah (Sotah 18a) discusses the oath of a Sotah, a woman suspected of adultery. The woman takes this oath when she drinks the "Mei Sotah," the special water which determines whether or not she was disloyal to her husband.
The Mishnah there says that she takes an oath that she did not sin at any stage of her marriage, while she was an "Arusah, Nesu'ah, Shomeres Yavam, or Kenusah." When, though, does she drink the Mei Sotah? The Mishnah cannot mean that she drinks the Mei Sotah when she is an Arusah, because an Arusah accused of adultery does not drink the Mei Sotah, as the Mishnah later states (Sotah 23b). Rather, the Mishnah must refer to a case in which her husband warned her ("Kinuy") not to isolate herself with another man while she was an Arusah, and she violated his warning and isolated herself with that man (Stirah). She then entered the Chupah with her husband and became a Nesu'ah (fully married). Her husband can obligate her to drink the Mei Sotah now because she is a Nesu'ah, even though his act of Nisu'in (Chupah) with her was an act of Nisu'in with a Pesulah (a woman he may not marry), since she was prohibited to him from the time of the Stirah. Accordingly, the Mishnah in Sotah is proof that "Yesh Chupah l'Pesulos," as Rav says.
The Gemara adds that an Arusah can become a Sotah only if she lived with her husband during Erusin before she sinned, because one of the conditions necessary for a woman to become a Sotah is that her husband must have had relations with her before the adulterer.
The Gemara challenges the proof from the Mishnah. The Mishnah is problematic in any case because it also states that a Sotah must take an oath that she did not sin while she was a Shomeres Yavam. It is not possible for a woman to have sinned while she was a Shomeres Yavam. Hence, no proof can be cited from that Mishnah.
The Gemara does not explain why it is not possible for a woman to be a Sotah while she is a Shomeres Yavam. RASHI (58b) presents two ways to understand the Gemara's statement. Rashi's words, however, are terse and need clarification. How does each approach understand the Gemara, and what is the differences between the two approaches?
In order to answer these questions, some words of introduction are necessary:
The Mishnah in Sotah (18a) states that a woman can become a Sotah for a suspected sin which she may have committed as an Arusah or Shomeres Yavam. This Mishnah, however, contradicts another Mishnah there (23b) which states that an Arusah and Shomeres Yavam are not eligible to drink the Mei Sotah.
The Gemara here answers that the first Mishnah (which states that an Arusah can become a Sotah) must refer to a case in which her husband warned her ("Kinuy") not to isolate herself with another man while she was an Arusah, and she violated his warning and isolated herself with that man (Stirah). After the Nisu'in (when she becomes fully married), her husband can obligate her to drink the Mei Sotah.
The Gemara addresses two problems with this answer:
A woman can become a Sotah only if she had relations with her husband before she sinned. If she violated his warning against Stirah when she was an Arusah or Shomeres Yavam, she did not yet have the opportunity to live with her husband and thus she should not be able to become a Sotah.
Moreover, in order to change her status from an Arusah or Shomeres Yavam to a Nesu'ah, the husband must perform Nisu'in with her through an act of Bi'ah. However, if she violated his warning against Stirah when she was an Arusah, she is prohibited to him. A man who has prohibited relations with his wife after her Stirah (when he is no longer "Menukeh me'Avon," or "clean of any wrongdoing" himself) cannot obligate his wife to drink the Mei Sotah.
These two problems may be expressed as two basic questions: How is it possible that the husband had relations with his Arusah before the adulterer did, and how is it possible that he had relations (to make her his wife through Nisu'in) after the adulterer did?
The Gemara resolves these two questions in a straightforward manner. The Gemara explains that the husband had relations with his Arusah before the adulterer -- he lived with her illicitly ("l'Shem Z'nus") when she was still in her father's home. As for how it was possible for the husband to have relations with her after the adulterer did, indeed it was not possible; he did not have relations with her after the adulterer did. In order to effect Nisu'in and make her a Nesu'ah, Bi'ah is not necessary. Chupah without Bi'ah also constitutes a valid Nisu'in, even when the Chupah is performed with a woman to whom he is prohibited (this is the proof for Rav that "Yesh Chupah l'Pesulos").
However, the Gemara does not resolve its questions about how a Shomeres Yavam could become a Sotah. It is at this point that Rashi offers two different explanations for the Gemara's question.
(a) RASHI'S FIRST EXPLANATION. Rashi explains that the Gemara seeks to clarify how the Shomeres Yavam could have had relations with the Yavam before the woman's Stirah. If she lived with the Yavam, she became his wife through Yibum and was no longer a Shomeres Yavam at the time of the Stirah. The Gemara suggests that perhaps the Bi'ah was done b'Shogeg or b'Ones; such a Bi'ah is not a valid form of Yibum to create Nisu'in (according to Shmuel) but only to create Erusin, and thus it is still possible to call her a Shomeres Yavam.
This answer does not suffice according to Rav (who says that a Bi'ah done b'Shogeg or b'Ones is valid in all respects), and thus the Gemara suggests another answer. The Gemara says that the Mishnah expresses the view of Beis Shamai and refers to a case in which the Yavam did Ma'amar. After Ma'amar, a Bi'ah done b'Shogeg or b'Ones is not a valid form of Yibum even according to Rav (as the Gemara mentions earlier on 29b). The Yavam's act of Ma'amar transforms the bond of Zikah into an Erusin-like bond which must culminate in Nisu'in. A Bi'ah done b'Shogeg or b'Ones during an Erusin-like bond cannot accomplish Nisu'in.
This explanation is problematic in two ways.
1. This approach does not address the Gemara's second question concerning a Shomeres Yavam: how can the Yavam perform Nisu'in (Yibum) with the Yevamah after her Stirah and yet remain "Menukeh me'Avon"? Bi'ah is the only way to marry her in this case (Yibum), but if he does Bi'ah he will not be "Menukeh me'Avon."
(One might argue that after Bi'ah is done b'Shogeg, a Shomeres Yavam can become a Sotah even without having done Yibum, since a partial Kinyan has been made. However, that partial Kinyan resembles Erusin, and a woman cannot become a Sotah during Erusin. Moreover, the Gemara in Sotah (24b) implies that a Shomeres Yavam cannot become a Sotah even after such a Bi'ah.)
TOSFOS (DH d'Kavasah) answers that the Mishnah in Sotah (18a) cited by the Gemara here expresses the opinion of Rebbi Yoshiyah (see Sotah 24b) who maintains that a Shomeres Yavam may drink the Mei Sotah even before she becomes a Nesu'ah. According to Rebbi Yoshiyah, it is not necessary for the Yavam to do Yibum with her before she may drink the Mei Sotah.
2. Another problem is that according to this explanation, the Gemara takes sides on an issue which was left unresolved earlier (29b): can Ma'amar (according to Beis Shamai) transform the Zikah into an Erusin-like bond and prevent Bi'as Shogeg from completing the Yibum? If the Gemara here decides that Ma'amar does transform the Zikah into an Erusin-like bond, it should have concluded as such earlier.
(b) RASHI'S SECOND EXPLANATION. Rashi explains that the Gemara addresses the second question: how can the Yavam marry the Shomeres Yavam through Yibum? A woman is eligible to drink the Mei Sotah only as a Nesu'ah. However, if the Yavam makes her his Nesu'ah by doing Bi'as Yibum with her, he is no longer "Menukeh me'Avon." The Gemara does not address the first question, how the husband is able to do Bi'ah with the Yevamah before the adulterer, because the Gemara understands that the Bi'ah which the original brother did with his wife (before he died) suffices to fulfill the condition that the "husband's Bi'ah precede the adulterer's."
The Gemara answers that according to Shmuel, the Yavam did Bi'ah b'Shogeg or b'Ones. (This does not mean that after the Stirah he did Bi'ah b'Shogeg or b'Ones and that he is "Menukeh me'Avon" because his act -- although prohibited -- was done b'Ones. If this were the case, the Gemara would not need to continue. Even according to Rav who maintains that Bi'as Ones constitutes a valid act of Yibum, the same explanation may be given to explain how the woman becomes a Nesu'ah while the Yavam remains "Menukeh me'Avon." Although she drinks the Mei Sotah when she is a Nesu'ah, the Mishnah calls her a "Shomeres Yavam" because the Kinuy and Stirah occurred while she was a Shomeres Yavam, as the Gemara suggests later (58b) with regard to an Arusah. Since the Gemara does not consider this an appropriate answer for the opinion of Rav, this answer must be understood in a manner similar to Rashi's first explanation, as follows.)
The Gemara means that the Yavam did Bi'ah b'Shogeg or b'Ones before the woman became a Sotah. Since she is not fully acquired by the Yavam with a Bi'as Shogeg or Ones (according to Shmuel), she still is called a "Shomeres Yavam." On the other hand, she can become a Sotah after a Bi'as Shogeg or Ones even though she still is a Yevamah, since she can be called "Tachas Ishech," in a state of matrimony, to a certain degree.
This explanation resolves the first problem with the first explanation of Rashi. According to this approach, the Gemara here clearly argues with the Gemara in Sotah (24b). The Gemara there says that a Yevamah cannot become a Sotah, even if Bi'as Shogeg or Mezid was done (this is the view of Rebbi Yonasan, who disagrees with Rebbi Yoshiyah as cited above). However, the Gemara there also states that the Bi'ah which the original brother did with his wife (before he died) does not suffice to fulfill the condition that the "husband's Bi'ah precede the adulterer's." It was this point which forces the Gemara there to conclude that after Bi'as Shogeg u'Mezid the Yevamah still cannot become a Sotah. Since the Gemara here disagrees in that respect, it is able to conclude that after Bi'as Shogeg u'Mezid the woman is able to become a Sotah and is considered "Tachas Ishech." (This approach also provides an answer to TOSFOS' questions on Rashi in Kidushin 27b, DH Hachi Garsinan.)
The Gemara concludes that even according to Rav, there is a way for the Yavam to be Koneh the Yevamah only partially, so that she is "Tachas Ishech" but not yet in the category of a Nesu'ah. This is accomplished through Ma'amar, according to Beis Shamai. Ma'amar with a Yevamah achieves a Kinyan similar to Nisu'in, as it gives the Yevamah the status of "Tachas Ishech." However, Ma'amar does not complete the Nisu'in until it is followed by Chupah, and thus she is still called a "Shomeres Yavam."
This explanation also resolves the second problem with Rashi's first explanation. The Gemara is not taking sides in the question of whether Bi'as Shogeg u'Mezid after Ma'amar is a valid Yibum. The Gemara here refers to Ma'amar which is not followed by Bi'as Shogeg u'Mezid; such a Bi'ah certainly does not serve to be Koneh a Yevamah completely (just as Erusin without Chupah does not serve to be Koneh a woman completely; see Rashi and Tosfos, 29b).
(This explanation leaves one matter unresolved. Rashi earlier (29b) writes that Ma'amar with a Yevamah is only a Kinyan d'Rabanan, even according to Beis Shamai. If Ma'amar is only mid'Rabanan, then mid'Oraisa she is not really a Nesu'ah after Ma'amar. How, then, can she drink the Mei Sotah after Ma'amar? According to Rashi's first explanation, since Bi'ah was done with the Ma'amar, it certainly effects a complete Kinyan mid'Oraisa and thus the Yevamah can become a Sotah. According to the second explanation, however, since Ma'amar was done without Bi'ah, why should the Yevamah be able to drink the Mei Sotah if, mid'Oraisa, she is not a Nesu'ah?)