Yevamot

If [the halizah was performed] after the three months, she need not wait three months.  Thus it may be inferred that the three months spoken of are [to be dated] from the time of the husband's death and not from the time of the levir's halizah. Why [is the law here]  different from that of a letter of divorce where Rab maintains [that the waiting period is to date] from the time of the delivery  and Samuel maintains [that it is to date] from the time of writing?  — Raba replied: A minori ad majus, if you permitted marriage  where a prohibition under the penalty of kareth is involved,  how much more so [should marriage be permitted  where only] an ordinary prohibition  [is involved]! SIMILARLY ALL OTHER WOMEN. The case of a sister-in-law  one can well understand, as has just been explained,  but why ALL OTHER WOMEN?  — R. Nahman replied in the name of Samuel: Because Scripture said, To be a God unto thee and unto thy seed after thee,  a distinction must be made between the seed of the first husband and the seed of the second. Raba raised an objection: Hence must a male proselyte and a female proselyte  wait three months.  Now, what distinction is there to be made here? — Here also there is the distinction to be made between seed that was sown in holiness and seed that was not sown in holiness. Raba said: This  is a preventive measure against the possibility of his  marrying his paternal sister,  contracting levirate marriage with the wife of his maternal brother,  setting his mother free to marry anybody  and releasing his sister-in-law to all the world. R. Hanania raised an objection: In all these  I read a provision against incest, but here  it is a provision in favour of the child.  Now, if this  is tenable, all  would be due to a provision against incest! — The meaning of 'a provision in favour of the child' is that the child might not infringe a prohibition of incest'. It is easy to understand why [a divorcee or widow] shall not marry after waiting a period of just two months because that would create a doubt as to whether the child is a nine-months one of the first  or a seven-months one of the second.  Let her wait, however, one month only and then marry, so that, should she give birth at seven months, the child would be a seven-months one of the last husband;  and should she give birth at eight months the child would obviously be a nine-months one of the first!  — Even if she gave birth at eight months it might still be assumed to be the child of the last husband since it may be that her conception was delayed one month. Let her, then, wait two months and a half and marry, so that, were she to give birth at seven months, the child would obviously be a seven-months one of the last,  and were she to give birth at six months and a half, the child would naturally be a nine-months one of the first;  for had he been the son of the last he would not be viable as a six-and-a-half-months child. — Even if she gave birth at six and a half months it is still possible to assume the child to be that of the last husband, for Mar Zutra stated: Even according to him who said that a woman who bears at nine months does not give birth before the full number of months had been completed,  a woman who bears at seven months 'does give birth before the full number of months has been completed;  for it is stated in Scripture, And it came to pass, after the cycles of days,'  the minimum of 'cycles'  is two, and the minimum of 'days' is two.  Let her, then, wait a little  and marry, and when the three months  will have been fulfilled she might be examined!  — R. Safra replied: Married women are not examined, in order that they may not become repulsive to their husbands. Then let her be examined by her walk!  — Rami b. Mama replied: A woman conceals the fact  in order that her child may inherit his share in her [second] husband's estate. Where, however, it has been ascertained that she  was pregnant, let her be permitted to marry! Why then was it taught: A man shall not marry the pregnant, or nursing wife of another;  and if he married, he must divorce her and never again remarry her! — This  is a preventive measure against the possibility of turning the foetus into a sandal.  If so, [this should apply in the case] of one's own wife also!  — If according to him who said, 'With an absorbent',  she uses  an absorbent; and if according to him who said, 'Mercy will be shewn from heaven',  mercy will be shewn from heaven. Here also  [it could be argued]: If according to him who said, 'With an absorbent', she uses an absorbent; if according to him who said, 'Mercy will be shewn from heaven', mercy will be shewn from heaven! — [The prohibition]  is due, rather, to [the danger of abdominal] pressure.  If so, [this  applies in the case] of one's own wife also!  — A man has consideration for his own.  Here also  one would have consideration for the child!  — [The reason is]  rather because a pregnant woman is usually expected to breast-feed her child [and were she to marry during pregnancy] she