There are two more topics where Beit Shammai was lenient and Beit Hillel was machmir (stringent). Number one: We mentioned earlier in the Masechet (tractate) how it worked in the times of the Mishnah: when a woman gave birth, she was teme'ah (impure)—if she had a boy, for seven days, and if she had a girl, for 14 days. Any bleeding she experienced after that—for 33 days for a boy and 66 days for a girl—is called dam tohar, pure blood. She is not considered to be a nida (menstruant) or a zavah (woman with abnormal bleeding), and her husband could technically be with her.
Here we’ll talk about what happens if she didn’t go to a mikveh (ritual bath), because even after she finishes the impure days, she has to go to a mikveh to experience those days of tohar (purity), or else she is still within her previous status. What is the status of the blood at that point if she didn’t go to the mikveh? Beit Shammai omrim—says Beit Shammai—the blood discharged during the tahor (pure) days of a Jewish woman who gave birth and did not dip in the mikveh when her days of tohar began is similar to her spit and urine. Those transmit teme'ah only when they’re moist, but not when they’re dried up. The blood here does not have the status of nida blood, which transmits teme'ah even after it has dried up. But the Hachamim (Sages) said that since the woman didn’t immerse in the mikveh after she gave birth, we’re going to treat the blood like the bodily fluids—spit, saliva, or urine—of a woman, which transmit teme'ah only while they’re moist. Beit Hillel omrim—says Beit Hillel—the blood transmits teme'ah when it’s moist or even after it dries.
The woman did not dip in a mikveh, so even though technically the tohar days were supposed to start, they only start if she actually went to the mikveh to dip and separate between the teme'ah—the days when she was teme'ah—and the days when she was a tahorah (ritually pure). Therefore, the blood is still considered to be the blood of childbirth, which does transmit teme'ah, whether it was moist or dry on a de'oraita (Torah law) level.
There is one case where Beit Shammai does agree that the blood is not considered to be tahor blood unless a woman dipped in the mikveh first. Beit Shammai agrees in the case of a woman who gave birth while she was a zavah: until she counted the seven clean days and then went into a mikveh, the blood she sees during her tahor days is still metame'ah, whether it’s moist or dry, because it’s the blood of a zavah.
With zivah (abnormal uterine bleeding), it works differently. It’s not just that a certain amount of time passes and then she can go dip in a mikveh, like a nida; no, when it comes to a zavah, she has to have clean days. If she never experienced those clean days, she went right from the bleeding days of the yoledet (woman who gave birth), when she gave birth, into the pure days of dam tohar. She never experienced that interim, that break where she could consider herself to be pure. Therefore, Beit Shammai would agree that in that case the blood is still considered to be yoledet blood, even afterwards, if it was during the days of dam tohar. It would therefore be metame'ah—it would make things impure with touch—whether it was dry or moist.