Niddah

Raba delivered the following discourse: A woman may wash her head on the Sabbath eve  and perform immersion at the termination of the Sabbath.  Said R. Papa to Raba: But did not Rabin send in his letter the message that 'a woman must not wash her head on the Sabbath eve and perform immersion at the termination of the Sabbath'? And, furthermore, is it not surprising to yourself that a woman should be allowed to  wash her head in the day time and perform immersion at night seeing that it is required that immersion should follow immediately after the washing of the head, which is not the case here? Raba subsequently appointed an amora  in connection with this matter and delivered the following discourse: The statement I made to you is an erroneous one,  but in fact it was this that was reported in the name of R. Johanan, 'A woman may not wash her head on the Sabbath eve and perform immersion at the termination of the Sabbath'; and, furthermore, it would be surprising that a woman should be allowed to  wash her head in the day time and perform immersion at night seeing that it is required that immersion should closely follow the washing of the head, which would not be the case here. But the law is that a woman may wash her head in the day time and perform immersion at night. And the law is that a woman may wash her head at night only.  But does not a contradiction arise between the one law and the other? — There is no contradiction: The former refers to a case where washing in the day time is possible while the latter refers to one where this is impossible. MISHNAH. IF A MENSTRUANT EXAMINED HERSELF ON THE SEVENTH DAY  IN THE MORNING AND FOUND HERSELF TO BE CLEAN, AND AT TWILIGHT  SHE DID NOT ASCERTAIN HER SEPARATION,  AND AFTER SOME DAYS SHE EXAMINED HERSELF AND FOUND THAT SHE WAS UNCLEAN, BEHOLD SHE IS  IN A PRESUMPTIVE STATE OF CLEANNESS.  IF SHE EXAMINED HERSELF ON THE SEVENTH DAY  IN THE MORNING AND FOUND THAT SHE WAS UNCLEAN, AND AT TWILIGHT  SHE DID NOT ASCERTAIN HER SEPARATION,  AND AFTER A TIME SHE EXAMINED HERSELF AND FOUND THAT SHE WAS CLEAN, BEHOLD SHE IS  IN A PRESUMPTIVE STATE OF UNCLEANNESS.  SHE  CONVEYS, HOWEVER, UNCLEANNESS FOR TWENTY-FOUR HOURS RETROSPECTIVELY OR DURING THE TIME BETWEEN THE LAST AND THE PREVIOUS EXAMINATION, BUT IF SHE HAD A SETTLED PERIOD, IT SUFFICES FOR HER TO BE DEEMED UNCLEAN FROM THE TIME OF HER DISCHARGE. R.  JUDAH RULED: ANY WOMAN WHO DID NOT,  FOLLOWING THE AFTERNOON, ASCERTAIN HER SEPARATION TO A STATE OF CLEANNESS IS REGARDED AS BEING IN A PRESUMPTIVE STATE OF UNCLEANNESS.  BUT THE SAGES RULED: EVEN IF SHE EXAMINED HERSELF ON THE SECOND DAY OF HER MENSTRUATION AND FOUND THAT SHE WAS CLEAN, AND AT TWILIGHT SHE DID NOT ASCERTAIN HER SEPARATION, AND AFTER A TIME SHE EXAMINED HERSELF AND FOUND THAT SHE WAS UNCLEAN, SHE IS REGARDED AS BEING IN A PRESUMPTIVE STATE OF CLEANNESS. GEMARA. It was stated: Rab ruled: She  is a certain zabah, but Levi ruled: She is a doubtful zabah. What do they refer to? If it be suggested: To the first clause [it could be objected]: Was it not stated, BEHOLD SHE IS IN A PRESUMPTIVE STATE OF CLEANNESS? If, on the other hand, they refer  to the final clause,  one can well see the logic of regarding the woman  as a doubtful zabah,  but why also  a certain zabah seeing that she has examined herself and found that she was clean?  The fact is that when the statements of Rab and Levi were made they were given as independent rulings:  If a menstruant examined herself on the seventh day in the morning and found that she was unclean, and at twilight she did not ascertain her separation, and after some days she examined herself and found that she was unclean, Rab ruled: She is a certain zabah, but Levi ruled: She is a doubtful zabah. 'Rab ruled: she is a certain zabah', since she was previously found to be unclean and now also she was found to be unclean, she must be definitely unclean. 'But Levi ruled: She is a doubtful zabah', because it might be assumed that the discharge may have been discontinued in the intervening time.