Niddah

GEMARA. It was stated: If a woman observed a discharge on the fifteenth day of one month, on the sixteenth of the next month and on the seventeenth of the third month, Rab ruled: She has thereby established for herself a settled period in arithmetical progression,  but Samuel ruled: No settled period can be established unless the progression is repeated three times.  Must it be conceded that Rab and Samuel differ on the same principle as that on which Rabbi and R. Simeon b. Gamaliel differ? For it was taught: If a woman was married to one man who died and to a second one who also died, she may not be married to a third one; so Rabbi. R. Simeon b. Gamaliel ruled: She may be married to a third but may not be married to a fourth?  — No, all  may concede that the law is in agreement with R. Simeon b. Gamaliel but it is this principle on which they  differ here: Rab holds that the fifteenth day is included in the number while Samuel holds that the fifteenth, since the observation on it was not in arithmetic progression, is not included in the number. He raised an objection against him: If a woman had been accustomed to observe her discharge on the fifteenth day  and this was changed  to the sixteenth, intercourse is forbidden  on both days.  If this was changed  to the seventeenth day, intercourse  on the sixteenth is again permitted  but on the fifteenth  and the seventeenth  it is forbidden. If  this was changed to the eighteenth intercourse  is again permitted on all the former dates;  and  is forbidden only on the day after  the eighteenth and onwards.  Now does not this  present an objection against Rab?  — Rab can answer you: Where a woman was accustomed to observe her discharge on a certain date  the law is different.  But as to him who raised the objection, on what possible ground did he raise it?  — [He assumed that the case of] one who was accustomed to a settled period had to be stated:  As it might have been presumed that since she was accustomed to observe her discharge on a settled date and this was changed, the change is effective  even if this  occurred only twice, hence we had to be informed [that  the change must have recurred three times]. An objection was raised: If she observed a discharge on the twenty-first day of one  month, on the twenty-second of the next month and on the twenty-third of the third month, she has thereby established for herself a settled period. If she skipped over  to the twenty-fourth  day of the month, she has not established for herself a settled period.  Does not this  present an objection against Samuel?  — Samuel can answer you: Here we are dealing with the case of a woman, for instance, who was accustomed to observe her discharge on the twentieth day and this  was changed to the twenty-first.  An inference from the wording also justifies this view;  for the twentieth day was left out  and the twenty-first was mentioned.  This is conclusive. FOR A WOMAN MAY NOT REGARD HER MENSTRUAL PERIOD AS SETTLED UNLESS THE RECURRENCE HAS BEEN REGULAR etc. R. Papa explained: This  was said only in regard to the establishment of a settled period,  but as regards taking the possibility of a discharge into consideration  one occurrence suffices.  But what  does he  teach us, seeing that we have learnt: IF SHE WAS ACCUSTOMED TO OBSERVE A FLOW OF MENSTRUAL BLOOD ON THE FIFTEENTH DAY AND THIS WAS CHANGED TO THE TWENTIETH DAY, MARITAL INTERCOURSE IS FORBIDDEN ON BOTH DAYS?  — If the inference had to be made from there,  it might have been presumed that the ruling  applied only where the woman was still  within her menstruation period,  but where she is not within her menstruation period  she  need not consider the possibility of a discharge,  hence we were informed  [that even in the latter case the possibility of a discharge must be taken into consideration]. NOR IS SHE RELEASED FROM THE RESTRICTIONS OF A SETTLED PERIOD etc. R. Papa explained: This, that it is necessary for the change to recur three times before a settled period can be abolished, was said only where a settled period had been established by three regular occurrences, but one that was established by two recurrences only may be abolished by one change. But what  does he  teach us, seeing that we learnt: A WOMAN MAY NOT REGARD HER MENSTRUAL PERIODS AS SETTLED UNLESS THE RECURRENCE HAS BEEN REGULAR THREE TIMES?  — It might have been presumed  that one occurence  is required for the abolition of one,  two  for two  and three  for three,  hence we were informed  [that even for two occurrences  only ones is required].  It was taught in agreement with R. Papa:  If a woman had a habit of observing her menstrual discharge on the twentieth day,  and this was changed to the thirtieth, intercourse is forbidden  on both days. If the twentieth day  arrived and she observed no discharge, she is permitted intercourse until the thirtieth but must consider the possibility of a discharge on the thirtieth day itself.  If the thirtieth day arrived and she observed a discharge, the twentieth  arrived and she observed none, the thirtieth arrived and she observed none and the twentieth  arrived and she observed one, the thirtieth  becomes a permitted day