Yevamot

— The other replied,  You have learned it: If one of them was a permitted wife and the other a forbidden one; if she submits to halizah he must submit to that of the forbidden one; and if he marries, he marries the permitted one. Now, what is meant by 'permitted' and 'forbidden'? If it be suggested that 'permitted' means permitted to all the world and 'forbidden' means forbidden to all the world, what practical difference, in view of the fact that she is in either case suitable for him, could this make to him? Consequently 'permitted' must mean permitted to him, and 'forbidden', forbidden to him; and this may happen where he remarries his divorced wife; and yet it was taught. 'If he marries he marries the permitted one'!  — No; 'permitted' may still mean permitted to all the world, and 'forbidden', forbidden to all the world; and as to your question. 'What practical difference, in view of the fact that she is in either case suitable for him, could this make'? One must take into account the moral lesson of R. Joseph. For R. Joseph said: Here, Rabbi taught that a man shall not pour the water out of his cistern so long as others may require it. Come and hear: 'Where a man remarried his divorced wife after she had been married, she and her rival are to perform halizah.' Is it possible to say 'she and her rival'? Consequently it must mean, 'either she or her rival.'  Did you not, however, have recourse to an interpretation? [You might as well] interpret thus: She is to perform halizah, while her rival may either perform halizah or be married by the levir. R. Levi b. Memel said in the name of Mar 'Ukba in the name of Samuel: The rival of a mema'eneth  is forbidden. To whom [is she forbidden]? If it be suggested, to the brothers,  [it may be retort ed], now that she herself  is permitted,  for Samuel said, 'If she refused one brother she is permitted to marry the other',  is there any question that her rival is permitted!  Hence [it means] to himself.  Wherein, however, does the mema'eneth  differ  that she is in consequence permitted to the other brothers? Obviously, in that she had taken no action in relation to them;  but her rival also had taken no action in relation to them!  — It is an enactment made to prevent marriage with the rival of one's daughter  who was a mema'eneth. Is, however, the rival of one's daughter who is a mema'eneth forbidden? Surely we learned, IF, HOWEVER, ANY AMONG THESE DIED, OR MADE A DECLARATION OF REFUSAL, OR WERE DIVORCED  [etc.] THEIR RIVALS ARE PERMITTED. Now, against whom was the declaration of refusal made? If it be suggested that she refused the husband, then this case is identical with that of a divorced woman.  Consequently it must refer to refusal of the levir!  — No; it may, in fact, refer to the refusal of a husband, but there are two kinds of divorce. Wherein, however, does the refusal of a husband differ?  Obviously in that she thereby annuls the original marriage; but when she refused the levir she has also annulled the original marriage! — [It differs] in respect of what Rami b. Ezekiel had learnt. For Rami b. Ezekiel learnt: If she  declared her refusal against the husband she is permitted to marry his father;  if against the levir, she is forbidden to his father.  From this it clearly follows that from the moment she becomes subject to the levirate marriage  she is looked upon as his  daughter-in-law; similarly here also  she is looked upon as the rival of his daughter from the moment she  becomes subject to the levirate marriage. Said R. Assi: The rival of a woman incapable of procreation is forbidden;  for it is said in the Scriptures, And it shall be that the firstborn that she beareth,  which excludes a woman incapable of procreation, since she does not bear.  R. Shesheth raised an objection: In the case where three brothers were married to three women who were strangers to one another, and one of them having died, the second brother addressed to her  a ma'amar  and died, behold these  must perform the halizah but may not marry the levir; for it is said, And one of them die [etc.] her husband's brother shall go in unto her,  only she  who is tied to one levir  but not she who is tied to two levirs;  and concerning this it was taught: R. Joseph said, 'This is the rival of a paternal brother's wife whose prohibition  is due to her double subjection to the levirate marriage,  a case the like of which we do not find through out the Torah'.  Now, what does the expression 'This is' exclude? Does it not exclude the rival of a woman incapable of procreation, who is permitted!  — No; it excludes the rival of a woman incapable of procreation who is forbidden. What, then, is meant by the expression, 'This is'?  — It is that in this case, where the subjection to the levirate marriage has caused the prohibition, her rival requires halizah; in the case, however, of a woman incapable of procreation even halizah is not required. What is the reason? — The prohibition of the one  is Pentateuchal;  that of the other only Rabbinical. We learnt; IF, HOWEVER, ANY AMONG THESE DIED, OR MADE A DECLARATION OF REFUSAL, OR WERE DIVORCED, OR WERE FOUND INCAPABLE OF PROCREATION, THEIR RIVALS ARE PERMITTED!  — This is no difficulty; the one  is a case where he  knew her defect  while the other  is a case where  he did not know of it.  The inference from our Mishnah also proves this; for it was stated WERE FOUND  and not 'were'. This proves it. Raba said: