Yevamot

R. Simeon said: Intercourse or halizah with the one of them  exempts her rival.  If, however, he  participated in halizah with her to whom [the second brother had] addressed the ma'amar, her rival is not exempt.  If he  married her  and died, and a [third] brother was subsequently born, or if a [third] brother was born, and subsequently he married her  and died, both [widows] are exempt from the halizah and the levirate marriage. If he married her  and [after that a third] brother was born and then he himself died, both widows are exempt from the halizah and the levirate marriage; this is the opinion of R. Meir. R. Simeon, however, said: Since, when he  came [into the world] he found her  permitted to him,  and she was never forbidden to him even for one moment, he  may take in levirate marriage whichever of them he desires or he may participate in the halizah with whichever of them he desires. Now, in accordance with whose view was the case in the latter clause  taught?  If it be suggested that it was taught in accordance with the view of R. Meir,  it might be observed that, as R. Meir draws no distinction between marriage that was followed by birth and birth that was followed by marriage, all these cases should have been combined in one statement!  Consequently it must have been in accordance with the view of R. Simeon who thus differs  only in the case where the levirate marriage was followed by birth'  but does not differ  where birth was followed by levirate marriage.  Our point is thus proved. The Master said, '[If] the second intended to address a ma'amar to his deceased brother's wife but before he was able to do so, a third brother was born while he himself died, the first widow is exempt as "the wife of the brother who was not his contemporary" and the second may either perform halizah or be taken in levirate marriage'. What is meant by 'he intended' and what by 'he was not able'? If he did it, it is an accomplished fact;  and if he did not do it, it is not an accomplished fact!  -In fact [this is the meaning:] 'He intended' with her consent and 'he was not able' with her consent but against her wish. This,  however, is not in agreement with the view of Rabbi. For it was taught: If a man addressed a ma'amar to his deceased brother's wife against her consent, Rabbi regards this as legal [betrothal].  But the Sages say, This is not a legal [betrothal]. What is Rabbi's reason? — He deduces [this form of betrothal] from the intercourse with the wife of a deceased brother; as the Intercourse with the wife of a deceased brother may be effected against her will  so may the betrothal of the wife of a deceased brother be effected against her will. And the Rabbis? — They deduce it from the usual form of betrothal;  as the usual betrothal can be effected with the woman's consent only so may the betrothal of a yebamah  be effected with her consent only. On what principle do they differ? — One Master  is of the opinion that matters relating to a yebamah should be inferred from matters relating to a yebamah and the Masters  are of the opinion that matters of betrothal should be inferred from matters of betrothal. 'If, however, he addressed a ma'amar to the widow, and subsequently a third brother was born, or if a third brother was born first and he  addressed the ma'amar to the widow subsequently and died, the first widow is exempt as "the wife of his brother who was not his contemporary" while the second must perform the halizah, though she may not be taken in levirate marriage. R. Simeon said: Intercourse or halizah with the one of them exempts her rival'.  What is R. Simeon referring to?  If it should be suggested, 'To the case where the third brother was born first and he  addressed the ma'amar subsequently's surely it has been stated, that where birth preceded marriage R. Simeon does not differ from the Rabbis!  — But [the reference is] to the case where the ma'amar was addressed first and the third brother was born subsequently. Hence, 'if he participated in halizah with her to whom [the second brother had] addressed the ma amar, her rival is not exempt', because  the [subjection of the] rival  is a certainty  while [the subjection of her] to whom the ma'amar had been addressed is doubtful,  and no doubt may over-ride  a certainty. R. Manasseh b. Zebid sat in the presence of R. Huna, and in the course of the session he said: What is R. Simeon s reason?  — 'What is R. Simeon's reason'! [Surely it is] as it has been stated: The reason is 'because when he was born he found her permitted to him, and she was never forbidden him even for one moment'!  But [the question rather is] what is the reason of the Rabbis?  -Scripture said, A/Id take her to him to wife, and perform the duty of a husband's brother unto her,  the former levirate attachment still remains with her.  But then what of the following  where we learned, 'If he  married her  she is regarded as his wife in every respect'  and [in connection with this] R. Jose b. Hanina said, 'This teaches