Yevamot

in the first clause the woman's confirmed status  [would subject her] to the levirate marriage while the majority principle  [would enable her] to marry any stranger;  and, though 'confirmed status' is not as important a factor as a majority, the minority of women who miscarry must be added to the 'confirmed status' so that the factors on either side are equally balanced;  hence  she MUST NEITHER MARRY AGAIN NOR CONTRACT LEVIRATE MARRIAGE. In the final clause, however, the woman's confirmed status  as well as the majority principle  [points] to [the permissibility of marriage with] any stranger,  so that [viable] males  constitute a minority of a minority;  and a minority of a minority is not taken into consideration even by R. Meir. MUST NEITHER MARRY AGAIN NOR CONTRACT LEVIRATE MARRIAGE etc. For ever?  — Ze'iri replied: [She waits] on account of herself three months  and on account of her associate nine,  and then she may, at all events,  perform halizah. R. Hanina said: On account of herself [she must wait] three months, but on account of her associate  for ever.  But let her perform halizah  at all events!  — Both Abaye b. Abin and R. Hanina b. Abin replied: This  is a preventive measure against the possibility that the child  might be viable  as a result of which  you would have to subject her to the necessity of a public announcement  in respect of the priesthood.  Well, let her be subjected to the necessity! — It may happen that someone would be present at the halizah and not at the announcement,  and he would form the opinion  that a haluzah was permitted to a priest. We learned: [If a woman states], 'A son was given to me [while I was] in a country beyond the sea' and she also asserts, 'My son died and afterwards my husband died', she is believed. [If she states, however], 'My husband died and afterwards my son died', she is not believed, but note is taken of her assertion and she must, therefore, perform halizah but may not contract levirate marriage.  Let it, however, be apprehended that witnesses might come and confirm her statement and that, as a result, you would subject her to the necessity of an announcement in respect of the priesthood! — R. Papa replied: [This refers to] a woman divorced.  R. Hiyya son of R. Huna replied: [It refers to one] who stated 'I and he  were hidden in a cave'. MISHNAH. [IN THE CASE OF] TWO SISTERS-IN-LAW  ONE OF WHOM  STATED, 'MY HUSBAND IS DEAD', AND THE OTHER ALSO STATED, 'MY HUSBAND IS DEAD', THE FORMER  IS FORBIDDEN  ON ACCOUNT OF THE HUSBAND OF THE LATTER,  AND THE LATTER IS FORBIDDEN  ON ACCOUNT OF THE HUSBAND OF THE FORMER.  IF THE ONE HAD WITNESSES  AND THE OTHER HAD NO WITNESSES,  SHE WHO HAD THE WITNESSES IS FORBIDDEN,  WHILE SHE WHO HAD NO WITNESSES IS PERMITTED.  IF THE ONE HAD CHILDREN AND THE OTHER HAD NO CHILDREN,  SHE WHO HAD CHILDREN  IS PERMITTED  AND SHE WHO HAD NO CHILDREN  IS FORBIDDEN.  IF THEY  CONTRACTED LEVIRATE MARRIAGES,  AND THE LEVIRS DIED, THEY  ARE FORBIDDEN [TO MARRY AGAIN].  R. ELEAZAR  RULED: SINCE THEY WERE ONCE PERMITTED TO MARRY THE LEVIRS  THEY ARE PERMITTED TO MARRY ANY MAN. GEMARA. A Tanna taught: If the one  had witnesses  and also children, and the other had neither witnesses nor children, both are permitted [to marry again]. IF  THEY CONTRACTED LEVIRATE MARRIAGES, AND THE LEVIRS DIED, THEY ARE FORBIDDEN [TO MARRY AGAIN]. R. ELEAZAR RULED: SINCE THEY WERE ONCE PERMITTED TO THE LEVIRS THEY ARE PERMITTED TO MARRY ANY MAN. Raba inquired: What is R. Eleazar's reason? Is it because he is of the opinion that a rival  is eligible to tender evidence in favour of her associate or is it because [he holds that] she would not  cause injury to herself?  What practical difference is there [between the two assumptions]?