Shammai says: for all women it suffices [to reckon] their [period of uncleanness from their time [of discovering the flow]. Hillel ruled: [their period of uncleanness is to be reckoned retroactively] from the [previous] examination to the [last] examination, even if this was many days. The sages say: [the law is] not like the words of these or the words of those, but [the women are deemed to have been unclean] during [the preceding] twenty-four hours when this lessens the period from the [previous] examination to the [last] examination, and during the period from the [previous] examination to the [last] examination when this lessens the period of twenty-four hours. For any woman who has a regular period it suffices [to reckon her period of uncleanness from] the time she discovers the flow. And if a woman uses rags when she has marital intercourse, this is like an examination which lessens either the period of the [past] twenty-four hours or the period from the [previous] examination to the [last] examination.

How [does the rule that] it suffices [to reckon her period of uncleanness from] the time she discovers the flow work? If she was sitting on a bed and was occupied with ritually clean objects and then she leaves [the bed] and then sees [blood flow] she is unclean but the objects are clean. Even though they have said that she conveys uncleanness for a period of twenty-four hours [retroactively] she counts [the seven days of her menstruation] only from the time she observed the flow.

Rabbi Eliezer says: there are four types of women for whom it suffices [to reckon] their [period of uncleanness from] the time [of their discovering the flow]. A virgin, A pregnant woman, A nursing woman; And an old woman. Rabbi Joshua says: I have only heard [the ruling applied to] a virgin, but the halakhah is in agreement with Rabbi Eliezer.

Who is regarded as "virgin"? Any woman who has never yet observed a blood flow, even if she is married. "A woman in pregnancy"? One whose fetus is notice. "A nursing woman"? Until she has weaned her child. If she gave her child to a nursing woman, if she weaned him, or if he died: Rabbi Meir says: she conveys uncleanness retroactively for twenty-four hours; But the sages say: it suffices for her [to reckon her period of uncleanness from] the time of her [observation of the flow].

Who is regarded as "an old woman"? Any woman over whom three "onot" have passed near the time of her old age. Rabbi Eliezer says: for any woman over whom have passed three onot it suffices [to reckon her period of uncleanness from] the time of her [observing a flow]. Rabbi Yose says: for a woman in pregnancy and a nursing woman over whom three onot have passed it suffices [to reckon their period of uncleanness from] the time of their [observation of the flow].

Although though they said [that for a woman who has a regular period] it suffices to reckon her period of uncleanness from the time she observes a flow, she should nevertheless examine herself [regularly], except for a menstruant or one who is sitting over pure blood. She should also use testing-rags when she has marital intercourse except when she is sitting over pure blood or when she is a virgin whose blood is clean. And twice [daily] she should examine herself: in the morning and at the [evening] twilight, and also when she is about to have sexual relations. Priestly women are subject to an additional restriction [for they should examine themselves] when they are going to eat terumah. Rabbi Judah said: [these must examine themselves] also after they have concluded eating terumah.