Niddah

Rab ruled: If a menstruant performs immersion at 'the proper time  she may do it only at night  but if she performs it after the proper time  she may do it either in the day time or at night.  R. Johanan ruled: Whether at the proper time or after the proper time a menstruant may perform immersion only at night, on account of the possibility of her daughter's following her lead.  Rab, moreover, also withdrew his ruling; for R. Hiyya b. Ashi citing Rab laid down: Whether at the proper time or after the proper time  a menstruant may perform immersion only at night on account of the possibility of her daughter's following her lead.  R. Idi ordained at Narash that immersion shall be performed on the eighth day  on account of lions.  R. Aha b. Jacob issued a similar ordinance at Papunia on account of thieves.  Rab Judah did the same at Pumbeditha on account of the cold. Rabbah  acted similarly at Mahoza on account of the guards of the city gates.  Said R. Papa  to Raba,  Consider: At the present time the Rabbis have put all menstruants on the same level as zabahs,  why then should they not allow them  to perform immersion in the daytime of the seventh day?  — This cannot be allowed on account of the following ruling of R. Simeon. For it was taught: After that she shall be clean,  'after' means after all of them, implying that no uncleanness may intervene between them; but R. Simeon stated: After that she shall be clean  implies that after the act  she shall  be clean, but the Sages have ruled that it was forbidden to do so in case she might thereby land in a doubtful situation. R. Huna ruled: A woman  may wash her head on a Sunday  and perform immersion on the following Tuesday,  since similarly she  is allowed to wash her head  on a Friday  and undergo immersion on the following Saturday night.  A woman may wash her head on a Sunday and undergo immersion on the following Wednesday, since similarly she  is allowed to wash her head  on a Friday  and undergo immersion in the night following a festival that occurred on a Sunday. A woman may wash her head on a Sunday and undergo immersion on the following Thursday, since similarly she may wash her head on a Friday and undergo immersion in the night following the two festival days of the New Year that happened to fall immediately after a Saturday. R. Hisda, however, stated: In all these cases  we rule as mentioned  but we do not draw the inference of 'since similarly'; for where [the avoidance of an interval] is possible an interval must be avoided,  and only where this is impossible  may an interval be allowed.  R. Yemar, however, stated: We may even draw the inferences of 'since similarly'  except in the case where a woman is permitted to wash her head on a Sunday and undergo immersion on the following Thursday, for the parallel of the night following the two festival days of the New Year that happened to fall immediately after a Saturday does not hold, since it is possible for the woman to wash her head and undergo immersion in the same night.  Meremar in his discourse laid down: The law is in agreement with R. Hisda  but  in accordance with the interpretation of R. Yemar. The question was raised: May a woman wash her head at night  and perform immersion the same night?  — Mar Zutra forbids this, but R. Hinena of Sura permits it. Said R. Adda to R. Hinena of Sura:  Did not the following incident  actually occur  to the wife of the exilarch Abba Mari? She having had some quarrel  R. Nahman b. Isaac proceeded to pacify her, and when she said to him, 'What is the hurry now?