Zavim, Chapter One, Mishnah One
1) If a man has seen one issue of zov:
a) Bet Shammai says: he is to be compared to [a woman] who observes day a for each day.
b) But Bet Hillel says: he is to be compared to one who has had a seminal emission.
2) Should he see [one day] and on the second it stopped, and on the third day he saw two [issues], or one [issue] that was as copious as two:
a) Bet Shammai says: he is a full zav.
b) But Bet Hillel says: he defiles those objects on which he sits or lies, and must also go into running water, but he is exempt from the sacrifice.
3) Rabbi Elazar ben Yehudah said: Bet Shammai agrees that in such a case he is not real zav.
4) What do they disagree about? The case of one who saw two [issues], or one [issue] that was as copious as two [on one day], and stopped on the second day, and on the third day he saw another [issue].
a) Bet Shammai says: he is a real zav;
b) But Bet Hillel say: he only defiles those objects on which he sits or lies, and must also go into running water, but he is exempt from the sacrifice.
Section one: The two houses disagree in this mishnah concerning a man who had one emission of discharge of zov (see intro for all terms). According to Bet Shammai his status is like a woman who had an emission of zivah one time. Such a woman must wait a day and if she is pure that day, she will be pure at the end of the day. If she sees zivah for three straight days then she will be a full zavah. So too a man who saw one issue of zov must wait a day to see if he sees another issue. If he does, he is a zav and he will retroactively defile everything he touched, laid upon or sat upon from the time he saw the first issue. One who shifts the zov itself is also defiled.
Bet Hillel says that a man who has had one issue of zov has the same status as one who has had a seminal emission. He does not defile things by laying on them or sitting on them and one who shifts the semen is not defiled. If he sees a second time, then he is a zav, but only from that point and onward.
Section two: As we learned in the introduction, a full zav is one who saw three issues in one day or one issue for three straight days. The two houses here debate concerning a man who saw three issues, but not in one day or in three straight days.
According to Bet Shammai this person is considered a full zav, for the first sighting of zov counts with the second two. Not only is he impure and must immerse in living water, but he is also liable to bring a sacrifice.
Bet Hillel says that the discharge on the first day does not count together with the discharges that came two days later. Therefore, he is considered as if he had seen discharge only twice. He defiles through lying or sitting and he must immerse in living waters (a live spring, not a mikveh), as must a zav, but he is not liable for a sacrifice.
Section three: Rabbi Elazar ben Yehudah disagrees with the version of this dispute contained in section two. According to him since he only saw zov once and then had a day in which he was pure, the sightings on the third day do not join the sighting on the first day.
Section four: Rabbi Elazar ben Yehudah says that the disagreement is concerning a slightly different situation. He saw zov twice on the first day, or one discharge that counted as twice. Now he is clearly a zav, although he is not yet liable for a sacrifice. If he sees discharge again on the third day, Bet Shammai says that since he is already a zav, this sighting joins with the first two and he is a full zav.
Bet Hillel maintains their opinion that unless he sees for three straight days or three times on one day, he is not a full zav.