Mishnah Niddah 4:5

בְּנוֹת כּוּתִים, נִדּוֹת מֵעֲרִיסָתָן. וְהַכּוּתִים מְטַמְּאִים מִשְׁכָּב תַּחְתּוֹן כָּעֶלְיוֹן, מִפְּנֵי שֶׁהֵן בּוֹעֲלֵי נִדּוֹת, וְהֵן יוֹשְׁבוֹת עַל כָּל דָּם וָדָם. וְאֵין חַיָּבִין עָלֶיהָ עַל בִּיאַת מִקְדָּשׁ, וְאֵין שׂוֹרְפִין עֲלֵיהֶם אֶת הַתְּרוּמָה, מִפְּנֵי שֶׁטֻּמְאָתָן סָפֵק: Samaritan girls are considered menstruating women from the time they lie in their cradle. And the Samaritan men impart ritual impurity to the lower bedding like the upper bedding, i.e., all layers of bedding beneath them are impure, and their status is like the bedding above a man who experiences a gonorrhea-like discharge [zav]: The status of both levels of bedding is that of first-degree ritual impurity, which can impart impurity to food and drink. This is due to the fact that Samaritan men are considered men who engage in intercourse with menstruating women. And they are considered men who engage in intercourse with menstruating women because Samaritan women observe the seven-day menstrual period of ritual impurity for each and every emission of blood, even for blood that does not render them impure. Accordingly, if a Samaritan woman has an emission of impure blood during the seven-day period, she will nevertheless continue counting seven days from the first emission. It is therefore possible that the Samaritan men will engage in intercourse with their wives while they are still halakhically considered menstruating women, as the seven-day period of impurity should have been counted from the emission of the impure blood. But one who enters the Temple while wearing those garments upon which a Samaritan had lain is not liable to bring an offering for entering the Temple in a status of impurity, nor does one burn teruma that came into contact with those garments, because their impurity is uncertain.

בְּנוֹת צְדוֹקִין, בִּזְמַן שֶׁנָּהֲגוּ לָלֶכֶת בְּדַרְכֵי אֲבוֹתֵיהֶן, הֲרֵי הֵן כְּכוּתִיּוֹת. פֵּרְשׁוּ לָלֶכֶת בְּדַרְכֵי יִשְׂרָאֵל, הֲרֵי הֵן כְּיִשְׂרְאֵלִית. רַבִּי יוֹסֵי אוֹמֵר, לְעוֹלָם הֵן כְּיִשְׂרָאֵל, עַד שֶׁיִּפְרְשׁוּ לָלֶכֶת בְּדַרְכֵי אֲבוֹתֵיהֶן: With regard to Sadducee girls, when they were accustomed to follow in the ways of their Sadducee ancestors their status is like that of Samaritan women, whose halakha was discussed in the previous mishna. If the Sadducee women abandoned the customs of their ancestors in order to follow in the ways of the Jewish people their status is like that of a Jewish woman. Rabbi Yosei says: Their status is always like that of a Jewish woman, until they will abandon the ways of the Jewish people in order to follow in the ways of their Sadducee ancestors.

דַּם נָכְרִית וְדַם טָהֳרָה שֶׁל מְצֹרַעַת, בֵּית שַׁמַּאי מְטַהֲרִים. וּבֵית הִלֵּל אוֹמְרִים, כְּרֻקָּהּ וּכְמֵימֵי רַגְלֶיהָ. דַּם יוֹלֶדֶת שֶׁלֹּא טָבְלָה, בֵּית שַׁמַּאי אוֹמְרִים, כְּרֻקָּהּ וּכְמֵימֵי רַגְלֶיהָ. וּבֵית הִלֵּל אוֹמְרִים, מְטַמֵּא לַח וְיָבֵשׁ. וּמוֹדִים בְּיוֹלֶדֶת בְּזוֹב, שֶׁהִיא מְטַמְּאָה לַח וְיָבֵשׁ: With regard to the blood of a menstruating gentile woman or a gentile zava, and the blood discharged by a female Jewish leper during the days of purity of a woman who gives birth, Beit Shammai deem them ritually pure, and Beit Hillel say: The halakhic status of the blood of the gentile woman is like that of her saliva and her urine, which impart impurity only while moist. Likewise, the blood discharged by a Jewish leper during the days of purity imparts impurity only when moist. With regard to the blood of a woman who gave birth and reached the conclusion of her days of impurity, i.e., seven days after giving birth to a male or fourteen days after giving birth to a female, but who did not yet immerse in a ritual bath, Beit Shammai say: Although she has yet to immerse in a ritual bath, the blood does not retain the halakhic status of menstrual blood. Rather, the status of the blood is like that of her saliva and her urine, and it imparts impurity only while moist. And Beit Hillel say: Since she did not immerse in a ritual bath, her blood is considered like that of a menstruating woman, and it imparts impurity whether it is moist or dry. And Beit Shammai concede to Beit Hillel in the case of a woman who gives birth as a zava, where the woman must count seven clean days from the conclusion of her days of impurity, that any blood she sees during those seven days imparts impurity whether it is moist or dry.

הַמַּקְשָׁה, נִדָּה. קִשְּׁתָה שְׁלשָׁה יָמִים בְּתוֹךְ אַחַד עָשָׂר יוֹם וְשָׁפְתָה מֵעֵת לְעֵת וְיָלְדָה, הֲרֵי זוֹ יוֹלֶדֶת בְּזוֹב, דִּבְרֵי רַבִּי אֱלִיעֶזֶר. רַבִּי יְהוֹשֻׁעַ אוֹמֵר, לַיְלָה וָיוֹם, כְּלֵילֵי שַׁבָּת וְיוֹמוֹ. שֶׁשָּׁפְתָה מִן הַצַּעַר, וְלֹא מִן הַדָּם: With regard to a pregnant woman who experiences labor pains, and they are accompanied by an emission of blood, her status is that of a menstruating woman. If she experienced these pains accompanied by emissions of blood for three consecutive days within the eleven days between periods of menstruation, during which time emissions of blood render a woman a zava, and she rested from labor for a twenty-four-hour period, i.e., the pangs subsided, and she then gave birth, it indicates that the emissions were not due to her imminent labor, and this woman is considered one who gives birth as a zava. This is the statement of Rabbi Eliezer. Rabbi Yehoshua says: She is considered a zava only if the pangs subsided for a twenty-four-hour period of a night and the following day, like Shabbat evening and its accompanying day. Additionally, she is considered a zava in a case where she rested from the pain of labor but not necessarily from the flow of blood. In other words, the presence of labor pangs determines whether this blood is due to labor or the impure blood of ziva. Accordingly, if the pangs cease for twenty-four hours, she is considered a zava even if blood was discharging continuously from when she experienced her labor pains.

הַמַּקְשָׁה בְתוֹךְ שְׁמוֹנִים שֶׁל נְקֵבָה, כָּל דָּמִים שֶׁהִיא רוֹאָה, טְהוֹרִים, עַד שֶׁיֵּצֵא הַוָּלָד. וְרַבִּי אֱלִיעֶזֶר מְטַמֵּא. אָמְרוּ לוֹ לְרַבִּי אֱלִיעֶזֶר, וּמַה בִּמְקוֹם שֶׁהֶחְמִיר בְּדַם הַשֹּׁפִי, הֵקֵל בְּדַם הַקֹּשִׁי, מְקוֹם שֶׁהֵקֵל בְּדַם הַשֹּׁפִי, אֵינוֹ דִין שֶׁנָּקֵל בְּדַם הַקֹּשִׁי. אָמַר לָהֶן, דַּיּוֹ לַבָּא מִן הַדִּין לִהְיוֹת כַּנִּדּוֹן, מִמַּה הֵקֵל עָלֶיהָ, מִטֻּמְאַת זִיבָה, אֲבָל טְמֵאָה טֻמְאַת נִדָּה: A woman who experiences labor pains within eighty days of giving birth to a female, e.g., she conceived during the sixty-six days of purity, or she initially conceived twins and she gave birth to a female and the birth of the second fetus was delayed, all blood that she sees is ritually pure, as she is currently within her days of purity. And this remains the halakha until the child emerges from the womb, at which point she is rendered impure as a woman who gives birth. And Rabbi Eliezer deems ritually impure the blood that occurs due to these labor pains. The Rabbis said to Rabbi Eliezer: And what, if in an instance where the verse was stringent with regard to blood emitted while resting, namely if a pregnant woman emits blood after her days of purity without any labor pains she is rendered impure, the verse was lenient with regard to blood that accompanies the labor pains; then in an instance where the verse was lenient with regard to blood emitted while resting, i.e., during a woman’s days of purity, is it not right that we will be lenient with regard to blood that accompanies the labor pains? Rabbi Eliezer said to them: When deriving a halakha by means of an a fortiori inference, there is a principle that it is sufficient for the conclusion that emerges from an a fortiori inference to be like its source. In other words, the status of blood emitted due to labor pains during her days of purity should not be more lenient than that of blood emitted due to labor pains after her days of purity. Rabbi Eliezer elaborates: Concerning what type of impurity was the verse lenient with regard to a woman who experiences an emission of blood due to labor pains? Concerning the impurity of ziva. But she may still be rendered ritually impure with the impurity of a menstruating woman. So too, if a woman experiences emissions of blood due to labor pains during her days of purity, she is rendered a menstruating woman.

כָּל אַחַד עָשָׂר יוֹם בְּחֶזְקַת טָהֳרָה. יָשְׁבָה לָהּ וְלֹא בָדְקָה, שָׁגְגָה, נֶאֶנְסָה, הֵזִידָה וְלֹא בָדְקָה, טְהוֹרָה. הִגִּיעַ שְׁעַת וִסְתָּהּ וְלֹא בָדְקָה, הֲרֵי זוֹ טְמֵאָה. רַבִּי מֵאִיר אוֹמֵר, אִם הָיְתָה בְמַחֲבֵא וְהִגִּיעַ שְׁעַת וִסְתָּהּ, וְלֹא בָדְקָה, הֲרֵי זוֹ טְהוֹרָה, מִפְּנֵי שֶׁחֲרָדָה מְסַלֶּקֶת אֶת הַדָּמִים. אֲבָל יְמֵי הַזָּב וְהַזָּבָה וְשׁוֹמֶרֶת יוֹם כְּנֶגֶד יוֹם, הֲרֵי אֵלּוּ בְּחֶזְקַת טֻמְאָה: For all the eleven days of ziva that follow the seven days of menstruation, a woman has the presumptive status of ritual purity, as it is unusual for her to experience bleeding on these days. If a woman sat and did not examine herself every morning and evening to determine whether she emitted blood and is impure, it makes no difference whether she failed to examine herself unwittingly or due to circumstances beyond her control, or even if she acted intentionally and did not examine herself; she remains ritually pure. She is rendered impure only if she examined herself and was found to have emitted blood. By contrast, if the time of her menstrual cycle arrived, when she is required to examine herself, and she did not examine herself, that woman is ritually impure, as it is typical for a woman to discharge blood at that time. Rabbi Meir says: If a woman was in hiding from danger, and the time of her menstrual cycle arrived and she did not examine herself on that day, that woman is pure, because fear drives away blood. There is therefore no concern that she might have emitted blood. But with regard to the seven clean days of the zav and the zava, and with regard to a woman who observes a clean day for a day she experiences a discharge during her days of ziva, if she fails to examine herself on those days, these women have a presumptive status of ritual impurity, as they already experienced a discharge.