Yevamot

it might have been assumed [that this holds good only] while she is alive but that after death the bond is broken,  hence it was taught that the levirate bond is not automatically  dissolved. May it be suggested that the following supports his view: 'If his deceased brother's wife died, the Ievir is permitted to marry her sister', which implies her sister Only but not her mother?  — The same law may apply even to her mother; but because he taught in the earlier clause, 'if his wife died he is permitted to marry her sister', in which case her sister only is permitted and not her mother, the latter being forbidden Biblically, he also taught in the latter clause, 'he is permitted to marry her sister'. R. Huna b. Hiyya raised an objection: IF HE ADDRESSED THE MA'AMAR TO HER AND DIED, THE SECOND MUST PERFORM HALIZAH BUT MAY NOT ENTER INTO THE LEVIRATE MARRIAGE.  The reason then  is because he addressed to her  the ma' amar, but had he not addressed a ma'amar to her,  the second also would have been permitted to enter into the levirate marriage with him. Now, if it be maintained that the levirate bond does exist,  the second, owing to this bond, would be the rival of the 'wife of his brother who was not his contemporary'!  — Rabbah replied: The same law, that the second must perform the halizah with, but may not be married to the levir, applies even to the case where no ma'amar was addressed to her;  and the ma'amar was mentioned only in order to exclude the view of Beth Shammai. Since they maintain that the ma'amar effects a perfect contract,  he teaches us [that it was not so]. Abaye pointed out the following objection to him:  In the case of two [contemporary] brothers one of whom died without Issue, and the second determined  to address a ma'amar to his deceased brother's wife  but before he managed to address a ma amar to her a third  brother was born and he himself died, the first  is exempt  as 'the wife of his brother who was not his contemporary' while the second  either performs the halizah or enters into the levirate marriage.  Now, if it be maintained that a levirate bond does exist,  the second, owing to this bond, would be the rival of 'the wife  of his brother who was not his contemporary'!  Whose view is this? It is that of R. Meir, who holds that no levirate bond exists. Does R. Meir, however, maintain that no Ievirate bond exists?  Surely we have learned: In the case of four brothers two of whom were married to two sisters, if those who were married to the sisters died, behold their widows perform the halizah but may not be taken in levirate marriage [by either of the levirs].  Now, if R. Meir is of the opinion that no levirate bond exists,  these would come from two different houses,  and one brother could marry the one while the other could marry the other! — The fact is that [R. Meir maintains that] no levirate bond exists; [but the levirate marriage is nevertheless forbidden] because he is of the opinion that it is forbidden to annul the precept of levirate marriages, it being possible that while one of the brothers married [one of the widowed sisters] the other brother would die,  and thus the precept of levirate marriages would be annulled. If, however, no Ievirate bond exists, let [also the precept of the levirate marriage] be annulled! For R. Gamaliel who holds that no levirate bond exists  also [maintains that] the precept of the levirate marriage may be annulled; as we learned; R. Gamaliel said, 'If she  made a declaration of refusal  well and good;  if she did not make a declaration of refusal let [the elder sister] wait until [the minor] grows up  and this one  is then exempt as his wife's sister'!  -The other  said to him: Are you pointing out a contradiction between the opinion of R. Meir and that of R. Gamaliel?  No [replied Abaye]; we mean to say this: Does R. Meir provide even against a doubtful annulment  and R. Gamaliel does not provide even against a certainty!  — It is quite possible that he who does not provide  makes no provision even against a certain annulment, while he who does provide  makes provision even against a doubtful annulment. Said Abaye to R. Joseph: Rab Judah's statement  is Samuel's;  for we learnt: