נדה נד

נדה נד

שׁוֹטוֹת נִינְהוּ? טוֹעוֹת נִינְהוּ! אֶלָּא תְּנִי: טוֹעוֹת.

actually misguided? Since they are in doubt as to their status, would it not be more accurate to say that they are mistaken? The Gemara answers: Rather, this is how one should teach the statement of Rabbi Yehoshua in the mishna: Instead of making provisions to remedy the uncertainties of the mistaken, come and remedy the uncertainties of the competent women.

דְּתַנְיָא: יוֹם אֶחָד טָמֵא, וְיוֹם אֶחָד טָהוֹר — מְשַׁמֶּשֶׁת שְׁמִינִי וְלֵילוֹ עִמּוֹ.

As it is taught in a baraita with regard to these competent women: What is the halakha in the case of a woman who consistently has the following pattern for each pair of days: One day she is impure, i.e., she experiences bleeding, and one day she is pure, she does not experience bleeding? In what manner is it permitted for her to engage in intercourse with her husband? She may engage in intercourse with her husband on the eighth day from the first time that she experienced bleeding and its accompanying night. At that time she is pure from her menstruation, as she immersed and purified herself on the night of the seventh day. It is permitted for her to engage in intercourse during the eighth day and the following night, as she will not experience bleeding until the ninth day.

וְאַרְבָּעָה לֵילוֹת מִתּוֹךְ שְׁמוֹנָה עָשָׂר יוֹם. וְאִם הָיְתָה רוֹאָה מִבָּעֶרֶב — אֵינָהּ מְשַׁמֶּשֶׁת אֶלָּא שְׁמִינִי בִּלְבַד.

In addition, she may engage in intercourse four nights out of the cycle of eighteen days, which consist of the seven menstrual days and the eleven days of the flow of the zava. This woman will never become a greater zava, as she does not emit blood on consecutive days. Since she must observe a day of purity during the eleven days of ziva each time she experiences bleeding, she may engage in intercourse with her husband on the night following the tenth, twelfth, fourteen, and sixteenth days. The night after the eighteenth day is considered part of the next cycle of menstruation and ziva. But if she sees blood in the evening, she may engage in intercourse with her husband only on the eighth night and its day. During the eleven days of ziva she either experiences bleeding at night or is observing a day of purity for the blood she had emitted earlier.

שְׁנֵי יָמִים טְמֵאִין, וּשְׁנֵי יָמִים טְהוֹרִין — מְשַׁמֶּשֶׁת שְׁמִינִי, וּשְׁנֵים עָשָׂר, וְשִׁשָּׁה עָשָׂר, וְעֶשְׂרִים.

If in every set of four days, two days she is impure, i.e., experiences bleeding, and two days she is pure, she may engage in intercourse with her husband on the eighth day, in the day or at night, and also on the twelfth day, after observing the eleventh as a day of purity for the sightings of the ninth and tenth days, and by a similar calculation on the sixteenth day and on the twentieth day, as she has not yet seen the blood of menstruation in this new cycle.

וּתְשַׁמֵּשׁ נָמֵי בִּתְשַׁסַר! אָמַר רַב שֵׁשֶׁת: זֹאת אוֹמֶרֶת, ״גַּרְגְּרָן״ דִּתְנַן — אָסוּר.

The Gemara objects: And let her also engage in intercourse with her husband on the nineteenth day, as the eleven days of the flow of the zava have already passed at the end of the eighteenth day, and she is no longer required to observe a clean day for each day she experiences a discharge. Rav Sheshet says: That is to say that when we learned in a mishna (72a) that a husband who could not wait for the conclusion of the day after the last day of ziva before engaging in intercourse is a glutton, it means that it is actually prohibited for them to engage in intercourse.

רַב אָשֵׁי אָמַר: נְהִי דְּחַד עֲשַׂר לָא בָּעֵי שִׁימּוּר, עֲשִׂירִי מִיהָא בָּעֵי שִׁימּוּר.

Rav Ashi says: In fact, it is not prohibited for a woman to engage in intercourse with her husband on the day after the end of the days of the flow of the zava even by rabbinic decree, as it is already the beginning of her menstrual days, and she is no longer required to observe a clean day for each day she experiences a discharge. But although there is no requirement to observe a clean day for the eleventh day of ziva, which is the eighteenth day of the full cycle, in any event there is a requirement to observe a clean day for the tenth day, i.e., the seventeenth of the entire cycle. Since she did not observe a clean day on the eighteenth day, as she saw blood on that day as well, she must observe the nineteenth day in purity.

שְׁלֹשָׁה יָמִים טְמֵאִין וּשְׁלֹשָׁה יָמִים טְהוֹרִין, מְשַׁמֶּשֶׁת שְׁנֵי יָמִים, וְשׁוּב אֵינָהּ מְשַׁמֶּשֶׁת לְעוֹלָם.

If out of every set of six days, three days she is impure, and three days she is pure, she may engage in intercourse with her husband during two of the days, and thereafter she may never again engage in intercourse with him. The eighth and ninth days, which are the first days of the flow of ziva, are the second and third of the three days on which she experiences bleeding. Therefore, she can immerse and purify herself on the night of the eleventh, and engage in intercourse with her husband on the eleventh and twelfth days. These are the only two days on which she is permitted to engage in intercourse with her husband, as afterward she will experience bleeding for three days during the days of the flow of the zava, and is thereby rendered a greater zava. Accordingly, she requires seven clean days to become pure again, which she will never attain, as she never has more than three clean days.

אַרְבָּעָה יָמִים טְמֵאִים, וְאַרְבָּעָה יָמִים טְהוֹרִין — מְשַׁמֶּשֶׁת יוֹם אֶחָד, וְשׁוּב אֵינָהּ מְשַׁמֶּשֶׁת לְעוֹלָם.

If out of every set of eight days, four days she is impure, and four days she is pure, she may engage in intercourse with her husband during one of the days, the eighth, after her purification for menstruation, as it is the last of her first set of four days without blood, and thereafter she may never again engage in intercourse with him, as she will be rendered a greater zava by experiencing bleeding on the next three days.

חֲמִשָּׁה יָמִים טְמֵאִים, וַחֲמִשָּׁה יָמִים טְהוֹרִין — מְשַׁמֶּשֶׁת שְׁלֹשָׁה יָמִים, וְשׁוּב אֵינָהּ מְשַׁמֶּשֶׁת לְעוֹלָם. שִׁשָּׁה יָמִים טְמֵאִין, וְשִׁשָּׁה יָמִים טְהוֹרִין — מְשַׁמֶּשֶׁת חֲמִשָּׁה יָמִים, וְשׁוּב אֵינָהּ מְשַׁמֶּשֶׁת לָעוֹלָם.

If out of every set of ten days, five days she is impure, and five days she is pure, she may engage in intercourse with her husband during three of the days, i.e., the eighth, ninth, and tenth, as she has completed her menstruation period and has not yet emitted the blood of ziva, and thereafter she may never again engage in intercourse with him. Similarly, if out of every set of twelve days, six days she is impure, and six days she is pure, she may engage in intercourse with her husband during five of the days, i.e., the eighth to the twelfth, and thereafter she may never again engage in intercourse with him.

שִׁבְעָה יָמִים טְמֵאִין, וְשִׁבְעָה יָמִים טְהוֹרִין — מְשַׁמֶּשֶׁת רְבִיעַ יָמֶיהָ, מִתּוֹךְ עֶשְׂרִים וּשְׁמוֹנָה יָמִים.

If out of every set of fourteen days, seven days she is impure, and seven days she is pure, she may engage in intercourse with her husband during a quarter of the days of her life, i.e., seven out of every twenty-eight days. In the first seven days she is a menstruating woman, but during the next seven days she is pure. In the third set of seven days, when she again experiences bleeding, she becomes a zava, which means that in her last seven days, which are without blood, she counts the clean days for her ziva, after which this cycle of twenty-eight days begins afresh.

שְׁמוֹנָה יָמִים טְמֵאִין, וּשְׁמוֹנָה יָמִים טְהוֹרִין — מְשַׁמֶּשֶׁת חֲמִשָּׁה עָשָׂר יוֹם מִתּוֹךְ אַרְבָּעִים וּשְׁמוֹנָה.

If out of every set of sixteen days, eight days she is impure, and eight days she is pure, she may engage in intercourse with her husband fifteen days out of every forty-eight days. The first eight days during which she experiences bleeding are the seven days of menstruation and one day of ziva, which renders her a lesser zava. Therefore, she must observe one clean day, after which she is pure for seven days. The first two days of the third set of eight are her last days of ziva, and the bleeding she experiences renders her again a lesser zava, while the next six are during her days of menstruation. Then she starts her fourth set of eight days, which are without blood. The first of these completes her days of menstruation, after which she may engage in intercourse for the subsequent seven days. During the fifth set of eight days she experiences bleeding, rendering her a greater zava. She counts her clean days in the sixth set, leaving her one day of purity, after which the cycle of forty-eight days starts again.

הָנֵי אַרְבֵּיסַר הָווּ!

The Gemara objects: But the days during which she is permitted are actually only fourteen, not fifteen. This objection is based on the assumption that a woman cannot count her clean days for ziva during days that are fit for menstruation. Consequently, the last four days of the fifth cycle are actually part of her days of menstruation, as her eleven days of ziva ended after the fourth day of that cycle. If so, the sixth set of eight days consists of three menstrual days followed by five days of ziva. Although she is not a menstruating woman in those three days, as she did not previously count seven clean days, they still do not count for her seven clean days of ziva, since they are fit to be menstrual days. She can start counting her seven clean days only on day forty-four, but on day forty-nine, before the seven clean days are finished, she will again experience bleeding. Therefore, it should not be permitted for her to engage in intercourse with her husband on the forty-eighth night.

אָמַר רַב אַדָּא בַּר יִצְחָק: זֹאת אוֹמֶרֶת, יְמֵי נִדָּתָהּ שֶׁאֵין רוֹאָה בָּהֶן עוֹלִין לִסְפִירַת זִיבָתָהּ, דְּאִיבַּעְיָא לְהוּ:

Rav Adda bar Yitzḥak says that this premise should be rejected: That is to say that her menstrual days on which she does not actually see blood do count toward her counting of her seven clean days of ziva. In other words, she begins counting the seven clean days during these menstrual days. As a dilemma was raised before the Sages with regard to this issue:

יְמֵי לֵידָה שֶׁאֵינָהּ רוֹאָה בָּהֶן מַהוּ שֶׁיַּעֲלוּ לִסְפִירַת זִיבָתָהּ?

What is the halakha in the case of a woman who gave birth when she was a zava? There are seven days of impurity following the birth of a son and fourteen days of impurity following the birth of a daughter, during which the mother is impure even if she did not experience bleeding. With regard to those days during this period on which she does not see blood, are they reckoned in the counting of her seven clean days required to become purified from the status of ziva?

אָמַר רַב כָּהֲנָא: תָּא שְׁמַע, רָאֲתָה שְׁנַיִם, וְלַשְּׁלִישִׁי הִפִּילָה, וְאֵינָהּ יוֹדַעַת מָה הִפִּילָה —

Rav Kahana says: Come and hear a baraita: A woman saw blood on two consecutive days during the period of ziva, and on the third day she miscarried, but she does not know what she miscarried, i.e., whether it was a stillborn human fetus for which a woman contracts the impurity of childbirth, or whether she discharged an amorphous piece of tissue. In addition, she does not know whether she emitted blood during the miscarriage.

הֲרֵי זוֹ סְפֵק זִיבָה, סְפֵק לֵידָה.

In such a case, it is uncertain whether she has the status of one who experienced ziva or whether she has the status of a woman who gave birth. If she gave birth to a fetus and did not emit blood, she is a woman after childbirth but not a zava. If the discharge was an amorphous piece of tissue and she saw blood, she is a zava. If it was a human fetus and she saw blood, she is one who gives birth as a zava. Finally, if she did not emit blood and it was a discharge of an amorphous piece of tissue, she is not obligated to bring an offering at all.

מְבִיאָה קׇרְבָּן, וְאֵינוֹ נֶאֱכָל, וִימֵי לֵידָתָהּ שֶׁאֵין רוֹאָה בָּהֶן — עוֹלִין לָהּ לִסְפִירַת זִיבָתָהּ.

Consequently, she brings an offering but it is not eaten by the priests, as it is uncertain whether it is an offering of ziva or an offering for her childbirth, or whether it is non-sacred. And the days of impurity following this uncertain birth, on which she does not see blood, are reckoned in the counting of her seven clean days required to become purified from the status of ziva. This resolves the dilemma raised by the Sages.

אָמַר רַב פָּפָּא: שָׁאנֵי הָתָם, כֵּיוָן דְּאִיכָּא לְמֵימַר יוֹלֶדֶת זָכָר הִיא, וְכֹל הָנֵי שִׁבְעָה יַתִּירֵי דְּקָיָהֲבִינַן לַהּ סָלְקִי לַהּ לִסְפִירַת זִיבָתָהּ.

Rav Pappa says that this does not resolve the dilemma, as it is different there, since it can be said that she is a woman who gave birth to a male, and it is only for that reason that all of these additional seven days that we give her due to the concern that she might have given birth to a female, which would render her impure for fourteen days, are reckoned in the counting of her seven clean days of ziva. But if it was certain that she gave birth to a female, those days after the birth would not count toward her period of ziva.

אֲמַר לֵיהּ רַב הוּנָא בְּרֵיהּ דְּרַב יְהוֹשֻׁעַ לְרַב פָּפָּא: בְּיוֹלֶדֶת זָכָר אִיכָּא לְסַפּוֹקֵי, בְּיוֹלֶדֶת נְקֵבָה לֵיכָּא לְסַפּוֹקֵי? אֶלָּא לָאו שְׁמַע מִינַּהּ עוֹלִין, שְׁמַע מִינַּהּ.

Rav Huna, son of Rav Yehoshua, said to Rav Pappa: Is there uncertainty that perhaps she is a woman who gave birth to a male, but there is no uncertainty that she might be a woman who gave birth to a female? In fact, both possibilities must be taken into account. And yet, despite the fact that she might have given birth to a female, these seven days are included in the counting of her seven clean days. Rather, isn’t it correct to conclude from it that such days are reckoned in the counting? The Gemara comments: Indeed, conclude from the baraita that these days do count.

תִּשְׁעָה יָמִים טְמֵאִין, וְתִשְׁעָה יָמִים טְהוֹרִין — מְשַׁמֶּשֶׁת שְׁמוֹנָה יָמִים מִתּוֹךְ שְׁמוֹנָה עָשָׂר.

The Gemara concludes its citation of the baraita: In the case of a woman whose set pattern is that nine days she is impure, i.e., experiences bleeding, and nine days she is pure, she may engage in intercourse with her husband during eight days out of eighteen. The last two days of the nine with blood are part of her ziva period, after which she must observe one clean day, leaving her with eight days when she may engage in intercourse before the cycle begins again.

עֲשָׂרָה יָמִים טְמֵאִין וַעֲשָׂרָה יָמִים טְהוֹרִים — יְמֵי שִׁמּוּשָׁהּ כִּימֵי זִיבָתָהּ, וְכֵן לְמֵאָה וְכֵן לְאֶלֶף.

In the case of a woman whose set pattern is that ten days she is impure and ten days she is pure, the number of days of her being permitted to engage in intercourse with her husband is equivalent to the number of days of her experiencing the flow of ziva. In the first seven days she is a menstruating woman, followed by three days of blood that render her a zava. She must count seven of the ten days without blood to be purified from her ziva, which leaves her three days in which she may engage in intercourse, exactly the same as the three days of ziva on which she saw blood. And so too, the same applies in the case of one hundred days, as she experiences bleeding of ziva for ninety-three days, and is subsequently permitted to her husband for ninety-three days, and so too in the case of one thousand days.

הֲדַרַן עֲלָךְ בָּא סִימָן.

מַתְנִי’ דַּם הַנִּדָּה, וּבְשַׂר הַמֵּת — מְטַמְּאִין לַחִין, וּמְטַמְּאִין יְבֵשִׁין. אֲבָל הַזּוֹב, וְהַנִּיעַ, וְהָרוֹק, וְהַשֶּׁרֶץ, וְהַנְּבֵלָה, (והשכבת) [וְשִׁכְבַת] זֶרַע — מְטַמְּאִין לַחִין, וְאֵין מְטַמְּאִין יְבֵשִׁין. וְאִם יְכוֹלִין לְהִשָּׁרוֹת וְלַחְזוֹר לִכְמוֹת שֶׁהֵן — מְטַמְּאִין לַחִין וּמְטַמְּאִין יְבֵשִׁין.

MISHNA: The blood of a menstruating woman and the flesh of a corpse transmit impurity by contact and by carrying when they are moist, and likewise transmit impurity when they are dry. But with regard to the gonorrhea-like discharge of a zav [ziva], and the mucus and the saliva of a zav, and the carcass of a creeping animal, and an animal carcass, and semen, all transmit impurity when they are moist but do not transmit impurity when they are dry. And if one could soak those dry substances in water and thereby restore them to their previous state, they transmit impurity when moist and transmit impurity when dry.

וְכַמָּה הִיא שְׁרִיָּיתָן? בְּפוֹשְׁרִין מֵעֵת לְעֵת. רַבִּי יוֹסֵי אוֹמֵר: בְּשַׂר הַמֵּת יָבֵשׁ, וְאֵינוֹ יָכוֹל לְהִשָּׁרוֹת וְלַחְזוֹר לִכְמוֹת שֶׁהָיָה — טָהוֹר.

The mishna asks: And how long is the process of soaking these substances that determines whether they can be restored to their previous state? This is referring to soaking them in lukewarm water for a twenty-four-hour period. Rabbi Yosei says: With regard to the flesh of a corpse that is dry and cannot be soaked to restore it to its previous state, it is ritually pure, in the sense that an olive-bulk of the flesh does not transmit impurity imparted by a corpse. But a ladleful of the flesh transmits the impurity of the decayed flesh of a corpse.

גְּמָ’ מְנָא הָנֵי מִילֵּי? אָמַר חִזְקִיָּה: דְּאָמַר קְרָא ״וְהַדָּוָה בְּנִדָּתָהּ״ — מַדְוֶהָ כְּמוֹתָהּ, מָה הִיא מְטַמְּאָה, אַף מַדְוֶהָ מְטַמְּאָה.

GEMARA: The mishna teaches that the blood of a menstruating woman transmits impurity by contact and by carrying both when moist and when dry. The Gemara asks: From where are these matters derived? Ḥizkiyya says: They are derived from a verse, as the verse states with regard to a menstruating woman: “This is the law of him that has an issue…And of her who experiences the flow of her menstrual impurity” (Leviticus 15:32–33). The verse compares the status of the menstrual flow to that of the menstruating woman. This teaches that the status of the menstrual flow is like the status of the woman herself: Just as she transmits impurity by contact and by carrying, so too, the menstrual flow transmits impurity by contact and by carrying.

אַשְׁכְּחַן לַח, יָבֵשׁ מְנָלַן? אָמַר רַבִּי יִצְחָק: אָמַר קְרָא ״יִהְיֶה״ — בַּהֲוָיָתוֹ יְהֵא.

The Gemara asks: We found a source for the impurity of the menstrual blood when it is moist, since it is called the menstrual flow; from where do we derive that dry menstrual blood also transmits impurity? Rabbi Yitzḥak says that the verse states with regard to menstrual impurity: “And if a woman should have an issue, and her issue in her flesh shall be blood, she shall be in her impurity seven days, and whoever touches her shall be impure until the evening” (Leviticus 15:19). The term “shall be” indicates that the blood shall remain in its impure status even once it is dry.

וְאֵימָא: הָנֵי מִילֵּי בְּלַח וְנַעֲשָׂה יָבֵשׁ, יָבֵשׁ מֵעִיקָּרוֹ מְנָלַן? וְתוּ, הָא דִּתְנַן: הַמַּפֶּלֶת כְּמִין קְלִיפָּה, כְּמִין עָפָר, כְּמִין שַׂעֲרָה, כְּמִין יַבְחוּשִׁין אֲדוּמִּים — תָּטִיל לַמַּיִם, אִם נִמּוֹחוּ טָמֵא, מְנָלַן? ״יִהְיֶה״ — רִבּוּיָא הוּא.

The Gemara objects: But one may say that this statement applies only to blood that was initially moist and subsequently became dry, as it retains its initial status. With regard to blood that was dry at the outset, from where do we derive that it too transmits impurity? And furthermore, this inference does not provide a source for that which we learned in a mishna (21a): In the case of a woman who discharges an item whose shape is similar to a type of shell, similar to a type of soil, similar to a type of hair, or similar to a type of mosquito, if such items are red, she should cast them into water to ascertain their nature. If they dissolved, it is blood, and the woman is impure. From where do we derive that even this type of blood is impure? The Gemara explains: The term “shall be” is an amplification, indicating that menstrual blood in all these forms is impure.

אִי מָה הִיא עוֹשָׂה מִשְׁכָּב וּמוֹשָׁב לְטַמֵּא אָדָם וּלְטַמֵּא בְּגָדִים, אַף דָּמָהּ נָמֵי עוֹשֶׂה מִשְׁכָּב וּמוֹשָׁב לְטַמֵּא אָדָם וּלְטַמֵּא בְּגָדִים? אַטּוּ דָּמָה בַּר מִשְׁכָּב וּמוֹשָׁב הוּא?!

The Gemara objects: If so, one can likewise infer the following: Just as she, a menstruating woman, renders an item designated for lying or sitting impure to the extent that it transmits impurity to a person and to the extent that that person transmits impurity to his garments, despite the fact that the garments did not come into contact with the couch, so too, her blood also renders items designated for lying or sitting impure to the extent that they transmit impurity to a person and to the extent that he transmits impurity to his garments, in the manner of a primary source of ritual impurity. The Gemara replies: Is that to say that the concepts of lying and sitting apply to her menstrual blood? These categories of impurity are limited to people.

וּלְטַעְמָיךְ, אֶבֶן מְנוּגַּעַת בַּת מִשְׁכָּב וּמוֹשָׁב הִיא, דְּאִיצְטְרִיךְ קְרָא לְמַעוֹטֵי? דְּתַנְיָא: יָכוֹל תְּהֵא אֶבֶן מְנוּגַּעַת עוֹשָׂה מִשְׁכָּב וּמוֹשָׁב, לְטַמֵּא אָדָם לְטַמֵּא בְּגָדִים.

The Gemara asks: But according to your reasoning that this category of impurity is limited to people, do the concepts of lying and sitting apply to a stone afflicted with leprosy, so that a verse was necessary to exclude it? As it is taught in a baraita: One might have thought that a stone afflicted with leprosy should render an item designated for lying or sitting impure to the extent that it transmits impurity to a person and to the extent that he transmits impurity to his garments.

וְדִין הוּא: וּמָה זָב, שֶׁאֵינוֹ מְטַמֵּא בְּבִיאָה, עוֹשֶׂה מִשְׁכָּב וּמוֹשָׁב לְטַמֵּא אָדָם לְטַמֵּא בְּגָדִים. אֶבֶן מְנוּגַּעַת, שֶׁמְּטַמְּאָה בְּבִיאָה, אֵינוֹ דִּין שֶׁמְּטַמְּאָה מִשְׁכָּב וּמוֹשָׁב לְטַמֵּא אָדָם לְטַמֵּא בְּגָדִים!

The baraita explains: And this ruling might be derived by logical inference: If one enters a house where there is a stone afflicted with leprosy he becomes impure, but one who enters a house together with a man who experienced a gonorrhea-like discharge [zav] does not become impure. One may therefore infer as follows: If a zav, who does not transmit impurity by entering a house, nevertheless renders an item designated for lying or sitting impure to the extent that it transmits impurity to a person and to the extent that that person transmits impurity to his garments, then with regard to a stone afflicted with leprosy, which does transmit impurity by entering a house, is it not logical that it renders an item designated for lying or sitting impure to the extent that it transmits impurity to a person and to the extent that he transmits impurity to the garments he is wearing?

תַּלְמוּד לוֹמַר ״הַזָּב״ — ״הַזָּב״ וְלֹא אֶבֶן מְנוּגַּעַת. טַעְמָא דְּמַעֲטַיהּ קְרָא, הָא לָאו הָכִי מְטַמְּאָה.

The baraita concludes: Therefore, the verse states: “Every bed upon which the zav lies shall be impure, and every item upon which he sits shall be impure” (Leviticus 15:4). The term “the zav” indicates that only the zav, and not a stone afflicted with leprosy, renders items designated for lying or sitting impure. The Gemara infers from the baraita: The reason a stone afflicted with leprosy does not transmit impurity to items designated for lying or sitting is that the verse excluded it, but were it not so, the stone would transmit impurity to items designated for lying or sitting, despite the fact that the concepts of lying and sitting do not apply to a stone.

וּמִינַּהּ: לָאו מִי אָמְרַתְּ ״הַזָּב״ — וְלֹא אֶבֶן מְנוּגַּעַת, הָכִי נָמֵי אָמַר קְרָא ״אֲשֶׁר הִיא יוֹשֶׁבֶת עָלָיו״ — הִיא, וְלֹא דָּמָהּ.

The Gemara replies that from this same derivation one can infer that menstrual blood does not render items designated for lying or sitting impure: Didn’t you say that the term “the zav” teaches that only the zav, and not a stone afflicted with leprosy, renders items designated for lying or sitting impure? So too, a verse excludes menstrual blood from this category of impurity, as the verse states: “And he if is on the bed, or on any item upon which she sits, when he touches it, he shall be impure until the evening” (Leviticus 15:23). The term “she” indicates that she, the menstruating woman, but not her blood, transmits impurity to items designated for lying or sitting.