Levi says that according to Bais Hillel there are 2 maayanos. My question relates to the braysa on 29b-30a about the woman who came and saw 3 clean weeks, then 10 weeks alternating. Bais Hillel agreed over there that the woman would not be permitted to her husband on day number 21. The gemara said that was because even if she would go to the mikveh on day 21, she couldn't live with her husband lest she see blood afterwards, still in day 21. But if Bais Hillel says there are 2 maayanos, then even if she saw blood later in day 21 and even if that were her last day of zivah, the blood would be from the other maayan and would not disrupt her seven clean days, so she should be able to live with her husband on day 21 without a safake.
The Gemara (Daf 29b) discusses the possibility of Tashmish during the fourth week. Rebbi Yosi b'Rebbi Chanina claims that the fact that Tashmish is prohibited proves that we do not follow the majority of cases here. A majority of women give birth to a viable child, but we cannot be certain that the To'ah did. Therefore, the blood that she sees after day 21 is not definitely Dam Tohar.
Ravin argues with Rebbi Yosi b'Rebbi Chanina, claiming that there is a different reason for prohibiting Tashmish. She may have given birth a long time ago, which would mean that her Dam Tohar ended before the fourth week.
With specific regard to your question, we may apply these Shitos to blood on day 21, also. According to Rebbe Yosi b'Rebbi Chanina, she may not have given birth to a viable child, and there may not be any Yemei Tohar. According to Ravin, the Yemei Tohar may have ended before day 21. The blood of day 21 may be Dam Nidah, and is not definitely Dam Tohar.
Kollel Iyun Hadaf
I just received an answer from Ya'akov Tavin to my question regarding how Levi would learn the sugya of the to'ah woman of daf 29b-30a. Thanks, but I don't think it really answers the question. Pleas let me ask again more clearly (I hope): The to'ah (29b) had three clean weeks when she came to us. According to both Bais Hilel and Bais Shammai she is not permitted to have tashmish on day 21, because she MIGHT see blood, and it is possible that day 21 is the last day of her 7 clean days if she gave birth to a girl in a state of zivus. But how does Levi explain this according to Bais Hillel?
If Bais Hillel in fact holds (as Levi says) that there are 2 maayanos, then even if she is in need of one more clean day (the 21st), even if she sees blood on the 21st it does not ruin her 7 clean days, because it comes from the other maayan. In other words, there are only 2 possibilities for day 21: a) it is the last day of the 7 clean days needed if she gave birth to a female in a state if zivus the day before we see her. If so, she should be able to have tashmish on day 21 according to Levi, because even if she were to see blood if would be from the other maayan and would not be tamay blood. The only reason the gemara said she could not have tashmish on day 21 is that we are worried she will see blood which will upset her 7-clean-day count, but according to Levi since this blood comes from the other maayan (since she gave birth 21 days ago and has not seen blood since) it should not ruin her count anyway. b) She is waiting to become a nidah, so there is no reason she should not have tashmish in anticipation of possibly seeing blood. Therefore, the braysa of the to'ah (29b) seems to me to be a refutation of the view of Levi which says that Bais Hillel holds 2 maayanos.
You are quite correct. We misunderstood your question. Your question is a truly excellent question -- why isn't the To'ah permitted to her husband on day 21 according to Levi?
We couldn't find your question in any of the commentaries on the daf. The only answer I can think of is that Levi holds like that Tana of "v'Shavin," as the Gemara says on Daf 36a, but that is not entirely satisfactory since (a) the Gemara there ought to have pointed that out, and (b) what about the Iba'is Eima that does not seem to want to make an argument between the Tana'im on Levi's point.
Thanks for sharing your thought-provoking question with us, I'll b'Ezras Hashem let you know if I find anything else on the subject!