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Charlotte Elisheva Fonrobert





Menstruant as Zavah: How the Laws of Niddah Developed





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Charlotte Elisheva Fonrobert





Menstruant as Zavah: How the Laws of Niddah Developed








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Menstruant as Zavah: How the Laws of Niddah Developed

Leviticus 15 describes two types of impure bleeding for women: menstruation (niddah), and bleeding that is “not during her menstrual period (zavah).” The Rabbis attempt to define the difference in an abstract manner, and in so doing, elide the two.


Menstruant as Zavah: How the Laws of Niddah Developed

Tractate Niddah 1897 Vilna Printing 

Leviticus 15 lists various types of impurities based on male and female genital emissions:

Male — The text begins by describing an impure genital “flow” (zav) for men (vv. 2-15)—perhaps a kind of venereal illness, and then moves on to typical seminal emissions (vv. 16-18).

  • Zav (זָב; “flow”)
ויקרא טו:יב אִישׁ אִישׁ כִּי יִהְיֶה זָב מִבְּשָׂרוֹ זוֹבוֹ טָמֵא הוּא.
Lev 15:2 When any man has a discharge issuing from his member, he is unclean.[1]
  • Semen (שִׁכְבַת זָרַע)
ויקרא טו:טז וְאִישׁ כִּי תֵצֵא מִמֶּנּוּ שִׁכְבַת זָרַע וְרָחַץ בַּמַּיִם אֶת כָּל בְּשָׂרוֹ וְטָמֵא עַד הָעָרֶב.
Lev 15:16 When a man has an emission of semen he shall bathe his whole body in water and remain unclean until evening.

Whereas the impurity of the seminal discharge is short term, lasting only until the evening, and is removed simply by washing, the zav’s process requires counting seven days after the flow has stopped and washing specifically in “fresh” or “running” water [2](מים חיים). Following this, the man must bring an offering to the sanctuary and receive atonement (vv.14-15).

The difference between the process of purification for seminal emission and for zav emissions is likely due to the Torah seeing the former as normal and healthy and the latter as abnormal and unhealthy.

Female — The same division occurs in the description of female genital emissions (though presented in reverse order). The text first discusses menstruation (vv. 19-24) followed by a discussion of non-menstrual flow (vv. 25-30).

  • Menstruation (niddah, נִדָּה)
ויקרא טו:יט וְאִשָּׁה כִּי תִהְיֶה זָבָה דָּם יִהְיֶה זֹבָהּ בִּבְשָׂרָהּ שִׁבְעַת יָמִים תִּהְיֶה בְנִדָּתָהּ…
15:19 When a woman has a discharge, her discharge being blood from her body, she shall remain in her menstrual state seven days…
  • Non-menstrual flow
ויקרא טו:כה וְאִשָּׁה כִּי יָזוּב זוֹב דָּמָהּ יָמִים רַבִּים בְּלֹא עֶת נִדָּתָהּ אוֹ כִי תָזוּב עַל נִדָּתָהּ כָּל יְמֵי זוֹב טֻמְאָתָהּ כִּימֵי נִדָּתָהּ תִּהְיֶה טְמֵאָה הִוא.
Lev 15:25 When a woman has had a discharge of blood for many days, not at the time of her menstruation, or when she has a discharge beyond her period of menstruation, she shall be impure, as though at the time of her menstruation, as long as her discharge lasts.

As we saw with the two male discharges, purification from the woman’s menstrual period is described succinctly in the opening verse: the impurity ends after seven days, the length of a “standard” period (or a bit longer). Purification from an abnormal, and ostensibly unhealthy discharge, however, is more complicated:

ויקרא טו:כח וְאִם טָהֲרָה מִזּוֹבָהּ וְסָפְרָה לָּהּ שִׁבְעַת יָמִים וְאַחַר תִּטְהָר.
Lev 15:28 When she becomes pure of her discharge, she shall count off seven days, and after that she shall be pure.

As with the male flow, she must wait until the discharge ends, then count seven days with no discharge; only then she is pure. Following this, she must bring an offering to the sanctuary to receive atonement (vv. 29-30).

Prohibiting Sex with a Woman Experiencing Flow

As scholars have long noted, Leviticus 15 does not assume that sex with a woman during her period is forbidden, but this prohibition does appear in Leviticus 18:19 and 20:18. And as these texts in Leviticus 18 and 20 make no distinction between different types of vaginal bleeding, one may fairly assume that whether the woman is menstruating or experiencing some other type of bloody flow,[3] sexual activity would be forbidden. Certainly, this is what the rabbis assume.

Rabbinic Halakha: Niddah and Zavah

Rabbinic halakha distinguishes between the laws regarding menstruation (niddah) and those about non-menstrual bleeding, what the rabbis call zavah, i.e., “flow,” the feminine form of the biblical term for unhealthy male genital flow, zav.

To tease out the differences between these halakhot, the rabbis came up with a number of innovations:

Three Days of Bleeding – The verse says that a woman is a zavah (to use the rabbinic term) if she bleeds for “many days” (יָמִים רַבִּים). How many days is many days? Based on a midrashic analysis of the phrase, the rabbinic answer is three days (Sifra, Metzora, Zavim5:8-10).

What happens if she bleeds for only one or two days? Here the rabbis invented an entirely new category called “a woman who watches one day for one day” (שומרת יום כנגד יום; m. Niddah4:7, m. Zavim 1:1). In short, this means that she must wait one clean day before purification.[4] This is a radical departure from the biblical text, which knows nothing of such a category.

Purification at Night – Throughout the chapter, Leviticus 15 assumes that a person washes during the day and that evening becomes pure. The standard trope is “he shall wash in water and be impure until evening” (וְרָחַץ בַּמַּיִם וְטָמֵא עַד הָעָרֶב). When it comes to the menstruant woman, however, the text says, “she shall remain in her menstrual state seven days” (שִׁבְעַת יָמִים תִּהְיֶה בְנִדָּתָהּ).

Thus, the rabbis state that unlike all other impure people, a niddah only purifies herself (i.e., immerses in the mikvah) at night (j. Shabbat 2:1, Megillah 2:5; b. Niddah 67b).[5] A zavah, on the other hand, would go about purification in the standard way, and immerse during the day on the seventh day of her counting, and be pure that evening.[6]

11 Days – Although the Torah is clear that zavah bleeding is either “not during her menstrual period” (בְּלֹא עֶת נִדָּתָהּ) or “continues after her period is over” (אוֹ כִי תָזוּב עַל נִדָּתָהּ), it never clarifies how one determines the time of her “proper period” (called veset in rabbinic Hebrew) and when bleeding is outside this time frame.

One would imagine that the answer to this question would be simple; a woman would know, more or less, when she expects her period to start, and alternatively, when something feels different. Nevertheless, the rabbis do not leave this to individual intuition but claim that the eleven days following the seven days of menstruation delineated in biblical law are the days of zivah (i.e., non-menstrual flow; m. Niddah 4:4, 4:7, and 10:8).

The Mishnah simply takes this rule for granted,[7] and a number of later rabbinic texts quote the saying that “the eleven days between one niddah and the next are halakhah le-Moshe mi-Sinai[8] (ואחד עשר יום שבין נדה לנדה הלכה למשה מסיני), but this a way of expressing a rule’s antiquity, not of explaining its origin.[9]

The Mysterious Eleven Days of Possible Zavah

The eleven-day rule is quite problematic, conceptually as well as empirically. It does not seem to correlate with any biological reality about menstruation, since the average woman’s cycle is closer to 28 days than 18 days.[10] The enigmatic “eleven-day” rule led to a sharp debate in the medieval period about what happens after this period ends and she has not had any bleeding.

18-Day Cycle (Maimonides)

In Maimonides’ understanding of the Mishnah, a woman’s cycle follows the pattern of 7 days of niddah – 11 days of zivah; 7 days of niddah – 11 of zivah, etc., starting from the day of her first period as a teenager (Mishneh Torah, Sefer Kedusha, “Issurei Biah” ch. 6:3-4; Kapih ed.):

כל שבעת הימים שנקבעה לה וסת בתחלתן הן הנקראין ימי נדתה, בין ראת בהן דם בין לא ראת. ומפני מה נקראין ימי נדה? מפני שהם ראויין לנדה וכל דם שתראה בהן דם נדה יחשב.
All seven days from when her first period was established are called “days of niddah,” whether she bleeds on them or not. Why are they called “days of niddah”? Because they are the days when her bleeding can define her as a niddah, and any bleeding she experiences on those days is considered niddah.
וכל אחד עשר יום שאחר השבעה הן הנקראין ימי זיבתה, בין ראת בהן דם בין לא ראת. ולמה נקראין ימי זיבה? מפני שהן ראויין לזיבה, וכל דם שתראה בהן דם זיבה יחשב. והזהר בשני שמות אלו שהם ימי נדתה וימי זיבתה.
All eleven days following the seven days are called the “days of zivah” whether she bleeds or not. Why are they called “days of zivah”? Because they are the days when her bleeding can define her as a zavah, and any bleeding she experiences on those days is consideredzavah. So be careful with these two terms, that is, “days of niddah” and “days of zivah.”
כל ימי האשה מיום שיקבע לה וסת עד שתמות או עד שיעקר הוסת ליום אחר תספור לעולם שבעה מתחלת יום הוסת, ואחריהן אחד עשר שבעה ואחריהן אחד עשר, ותזהר במנין כדי שתדע בעת שתראה דם אם בימי נדה ראת או בימי זיבה, שכל ימיה של אשה כך הן שבעה ימי נדה וי”א ימי זיבה…
All the days of a woman’s life, from the day of her first period till the day she dies or her period switches to a different day, she will count seven from the beginning of that (first) period, and afterwards eleven, seven, then eleven. Be careful with this counting, so that you can know when she bleeds whether it is occurring on her days of niddah or days of zivah, for this is how a woman’s life is: seven days of niddah and eleven days of zivah

Considering the typical biological cycle of approximately twenty-eight days, this theory is unworkable, for how does this halakhic cycle map onto a biological cycle? For the average woman, every other menstruation would be considered irregular, zivah, bleeding with the consequent requirement for seven clean days, etc. Obviously, Maimonides is working with an abstract concept of niddah and zivah that bears very little relationship with the biblical juxtaposition of (normal) menstruation with (abnormal) non-menstrual bleeding.[11]

A Period of Potential Niddah

The majority of medieval scholars understood the eleven days as a restrictive category. That is, a woman’s bleeding is considered zivah only if it occurs during the first eleven days after a woman’s regular (i.e., biblical) “days of niddah.” Thus, any bleeding that occurs after this 18-day period is over is automatically considered the beginning of her next period (whether it is or not). This interpretation avoids forcing women to be zavot every other month, but it still makes little biological sense.

However the category of eleven days is understood, it has the effect of taking the determination of whether she is menstruating or whether something is wrong out of the woman’s hands and of putting it into an artificial rubric of counted days.

The Problem of Keeping Track

Given that the laws of purification for niddah and zivah are quite different, and that until she is purified, the couple’s sexual activity must be curtailed, one might imagine that figuring out where a given woman is in her 7-11 cycle would have been a high priority for a married couple and the rabbis who would advise them. It would seem that early on, the rabbis, and those Jews who followed their rulings, were having trouble with this system of counting.[12]

For instance, the Babylonian Talmud recounts the following tradition (b. Niddah 66a):

אמר רב יוסף אמר רב יהודה אמר רב, התקין רבי בשדות: ראתה יום אחד – תשב ששה והוא, שנים – תשב ששה והן, שלשה – תשב שבעה נקיים.
Rav Joseph said in the name of Rav Yehudah, who in turn said in the name of Rav: “Rabbi [Judah HaNasi] enacted in sadot (“rural communities” or possibly the name of a town): If a woman bleeds for one day, she should count that day plus six more. If she bleeds for two days, she should count those two days, plus six more; if she bleeds for three days, she should sit for seven “clean” (days)[13] [after the bleeding stops].”

According to this account, Rabbi Judah HaNasi assumed that women in rural communities (or in the community of Sadot) could not keep track of their periods, at least not the way the rabbis define them, and thus, he created a new rule for them: Every bleeding is treated as if it is both niddah and zivah.

The most significant aspect of this rule is that whenever a woman bleeds for three days – which is almost certainly going to be the case for every period – she must wait seven “clean” days after the bleeding ends before purifying herself in a mikvah, as if she were also a zavah. Not only does this go against the letter and spirit of the biblical law, but it creates serious hardship for the couple. But this, apparently, was the cost of complex and artificial interpretation of the verses offered by the rabbis.[14]

Treating Even a Drop of Blood as Both Niddah and Zavah

The next line of this passage offers an even more extreme example of eliding the two types of bleeding (b. Niddah 66a):

אמר ר’ זירא: בנות ישראל החמירו על עצמן, שאפילו רואות טפת דם כחרדל – יושבות עליה שבעה נקיים.
Rabbi Zeira said: “The ‘daughters of Israel’ imposed a stringency upon themselves that they would wait out seven clean (days) even if they saw a drop of blood the size of a mustard seed only.”[15]In this version of the practice, every bleeding, no matter when or for how long, is automatically treated as if the woman were both a niddah and a zavah.

The Custom of Jewish Women?

The most intriguing aspect of this “report” is that it is not about the legislation of a rabbi, as we saw in the above statement about Rabbi Judah HaNasi, but is attributed to the initiative of women themselves. If the attribution of this shift in practice to women is accurate, which is unknown,[16] why would women choose to do so?

Perhaps, as we saw with the tradition about R. Judah HaNasi, the women were simply concerned about miscounting their cycles, since according to rabbinic law, their cycles would be determined by the artificial cycle of 7- and 11-day periods of time.

And yet, another advantage of eliminating the distinction between niddah and zivah is that by circumventing the complex and rabbinic system and going with a “one size fits all”niddah/zivah for every period, the woman would no longer be dependent on consultation with a rabbinic sage.

Why So Strict?

The advantages of eliminating the distinction between niddah and zivah could only be accomplished by adding more days to a woman’s monthly calendar where she and her husband are forbidden from being intimate. Perhaps (some) women may simply have felt that the extra pious way is the safest way to avoiding accidental transgression. In addition, it is possible that some of them may have been more than happy to restrict their own sexual accessibility to their husbands beyond the biblical limit, or at least, weren’t bothered by doing so.

The Return of the Niddah and Zavah Distinction in Modern Times

Whatever its reason and origin, this practice of eliding niddah and zavah became the norm in Jewish law and is codified by all the standard medieval halakhic works, including the Shulchan Arukh (Yoreh Deah, 183:1).[17] Nevertheless, modern times have seen some pushback in certain communities, whether because of cases of halakhic infertility[18] or because modern couples find the extension of abstinence too much of a hardship.[19]

Thus, some observant Jews have decided to return to a form of “biblical law,” towards a “friendlier” form of sexual discipline. And yet, this biblical observance remains rabbinic in nature since all the details of hilkhot niddah, such as the definition of zavah as three days, the eleven days of zivah, and even requirement of purification through mikvah,[20] are all based on rabbinic interpretation and not the Bible itself.


April 18, 2018


Last Updated

October 27, 2023


View Footnotes

Prof. Charlotte Elisheva Fonrobert is Associate Professor of Jewish Studies in the Department of Religious Studies at Stanford University and is (returning) Director of Stanford’s Taube Center of Jewish Studies. She received her Ph.D. from Berkeley GTU, Center for Jewish Studies. She is the author of Menstrual Purity: Rabbinic and Christian Reconstructions of Biblical Gender, and co-editor of The Cambridge Companion to the Talmud and Rabbinic Literature and Talmudic Transgressions.