Historical development of family purity laws

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Judaism has rules for making every area of life kadosh, holy. We have rules for days of the week (Shabbat vs other days), eating (kosher vs non kosher), and even human sexuality – taharat ha’mishpacha (טהרת המשפחה pathways of family purity)

Jewish teachings on taharat ha’mishpacha, sexuality and holiness.

However, over the milennia, the Torah’s teachings on this subject have increased in stringency. In the time of the Bible, women and men did not have sex during a woman’s menses, for reasons of ritual purity (which has nothing to do with a woman being considered ‘unclean’; ritual purity laws affected both men and women, in a wider variety of contexts, see the above page for details.)  But by the time of the Babylonian Talmud (mostly edited by around 600 CE) confusion about the issue arose among some rabbis making rules on this topic.  An extra 7 days of waiting, after menstruation ended, was added to the time that a couple should not have sex. It was initially only a custom of the pious. Its incorporation into Jewish law stemmed from the confusion of rabbis over the duration of menstrual cycles.

Below we find Professor David Kramer’s groundbreaking study on this topic.



A Developmental Perspective on the Laws of Niddah, By David Kramer
David Kramer JTS

Dr. Kraemer is the Joseph J. and Dora Abbell Librarian and professor of Talmud and Rabbinics at The Jewish Theological Seminary.

This article was originally published in Conservative Judaism, Vol. 38(3), p.26-33, Spring 1986.

Jewish law has thrived through history as a consequence of interpretation and development. Because of its flexibility, the law was not restricted to the specific concerns of the Torah, and even laws of great difficulty or obscurity could be adapted to the dictates of an ever-changing reality. Among the most outstanding examples of radical development is the institution of niddah—the ritual impurity of women during their menstrual flows.

But unlike the vast majority of cases of halakhic development, the modern law of niddah stands in blatant contradiction to the spirit of the original Torah text. For this reason it is particularly interesting as a case study in development. A review of its evolution, beginning with the Torah and progressing through the Rabbinic period, follows below.

Niddah in the Torah


The Torah clearly delineates the rules by which a woman or man becomes ritually impure by virtue of a “flow,” and how that condition is to be reversed.
When any man has a running issue out of his flesh, because of his issue he is unclean (Lev. 15:2).

And when he that has an issue is cleansed of his issue then he shall number to himself seven days for his cleansing… (Lev. 15:13)

And if semen goes out from a man, then he shall bathe all his flesh in water, and be unclean until evening. (Lev. 15:16)

And when a woman has an issue, and in her flesh be blood, she shall be seven days in her menstrual separation… (Lev. 15:19)

And if a woman has an issue of her blood many days not in the time of her menstruation, or if it run beyond the time of her menstruation, all the days of the issue of her uncleanness shall be as the days of her menstruation: she shall be unclean…. (Lev. 15:25)

But if she be cleansed of her issue, then shall she number to herself seven days, and after that she shall be clean. (Lev. 15:28)

A man or a woman who experiences an unnatural flow becomes unclean. For a man no minimum requirement is described; any “running issue” seems to be sufficient to impart purity. If such a genital flow has occurred the man must count seven clean days before he can perform the cleansing ritual. However, because a woman naturally experiences certain monthly flows, she must “have an issue of her blood many days not in the time of her menstruation” to reach the state of impurity for which she requires seven clean days. As a result of menstruation itself, though, a woman becomes unclean for only seven days from her first flow. For an unnatural issue the individual must bring a sacrifice at the end of the clean period; following menstruation no sacrifice is required.

Menstruation, the Torah recognizes, is a natural bodily function. For that reason the stringencies pertaining to unnatural flows do not apply. That menstruation is considered natural is evident from the structure of the text. The Torah’s account of these laws uses the common chiastic structure (A-B-B-A, where A = unnatural flows and B = natural flows). Menstruation, here equated with seminal emission, is clearly the less severe of the potential flows which a woman might experience.

Rabbinic Expansion

(Sources for what follows, where not otherwise indicated, can be found in Maimonides, Issurei Biah, chapters 6 and 11, and in his respective sources.)

According to the midrash halakhah, as repeated variously in the gemara Niddah (especially the last two pages), a woman who begins to menstruate is impure for seven days regardless of the actual duration of her flow (cf. Lev. 15:19). If her period lasts three days, she is unclean seven.

Following that period she may immerse immediately, without waiting seven clean days.

If her period lasts longer than seven days she must count one clean day for each that has exceeded the seven.

If her blood flow continues for “many days” (Lev. 15:25), that is—according to the Rabbis—three days not during the time of her period, then she becomes unclean to a greater degree.

A man’s uncleanness is dependent upon “sightings,” a woman’s upon the counting of these three days. Therefore, if a man witnesses two flows in a single day (three to require a sacrifice) he becomes severely impure. A woman, on the other hand, may witness dozens of flows in a single day and still not acquire the state of severe impurity until she witnesses an issue for three consecutive days. Only after this has occurred is she required to count seven clean days prior to immersion.

Of course, these conditions do not describe practice today. The cause of the present stringencies is a matter of dispute in interpretation. It is impossible to understand the development of the law, however, without examining this dispute in some detail.

“The eleven days between one period And the next”

The Torah recognized a seven-day duration for a woman’s menstruation. Regarding the lapse between one menstrual period and the next it says nothing, aware, apparently, that a woman’s menstrual cycle is quite individual. The Rabbis, however, possess a tradition which suggests that there are eleven days between one menstruation and the next. Maimonides reads this phrase literally and suggests that a complete cycle is eighteen days (!) by definition.

The Rabbis, of course, could not have conceived of this cycle in so literal a manner. They were, after all, married to women whose monthly periods recurred, on the average, approximately every twenty-eight days. Rabbinic sources, too, reflect a familiarity with the realistic norm. At Niddah 9b R. Laqish reports in the name of R. Judah Nesiah that an average cycle lasts thirty days. Rashi there explains the cycle in this manner: “The days of impurity are ten—seven for menstruation and three for ‘unnatural flow,’ and twenty days of purity.”
Pages of Talmud

While his explanation is admittedly problematic, he clearly recognizes that, on the average, the days of purity (i.e. between periods) are twenty and not eleven. Even Maimonides recognizes that eleven days is not the norm, suggesting in his commentary to the Mishnah (to Niddah 38b) that eleven days is the very shortest time that might normally pass between one menstruation and the next. Yet, according to Maimonides, the eighteen-day “rabbinic cycle” became determinant for purposes of the laws of Niddah, and as a consequence of this institution, and the so-called “confusion” which it engendered (see below), practice moved unavoidably in the direction of stringency.

The gemara (Niddah 72b) reports in the name of R. Elazar ben Azariah that the “eleven days between one period and the next is a law (halakhah) to Moses from Sinai.” This supposed origin is challenged, however, on the basis of a quotation from the Sifra which derives this eleven day period in typical midrashic fashion. To resolve the apparent conflict, the gemara concludes that “to R. Akiba it is scriptural, to R. Elazar ben Azariah it is halakhah.”

Leaving aside for a moment the problem of the source of these eleven days, it is essential to recognize their effect according to Maimonides’ interpretation.


A woman’s cycle, he explains, must be counted in the following fashion. From the very first time she sees blood she must count seven days of her cycle, followed by eleven days during which an issue brings severe uncleanness, followed by another seven days followed by eleven, and so forth. This counting regards her natural cycle as absolutely irrelevant!

Assume a woman had a twenty-eight day cycle (an approximate norm). Her first seven day period would initiate her cycle.

The ovarian cycle is divided into the follicular and luteal phases, while the uterine cycle is divided into menstruation and the proliferative and secretory phases.
The ovarian cycle is divided into the follicular and luteal phases, while the uterine cycle is divided into menstruation and the proliferative and secretory phases.

By the time her next period began, however—twenty-one days after the end of her first—another eleven and then seven days would have passed in her Jewish cycle, and her natural menstruation would then occur during what the Rabbis considered a non-menstrual time, rendering her severely impure and requiring seven clean days before her immersion.

Despite the extreme difficulty and confusion which this cycle would impose, Maimonides claims that at one time Jewish women counted these cycles very carefully, and acted appropriately depending upon the correspondence of their own periods to this cycle.

Problems were bound to develop, of course, and in order to be “safe” Rav relates that Rabbi Judah the Prince (end of second century C.E.) instituted certain stringencies which would help prevent mistakes (Niddah 66a and Rashi there).

Finally, Rabbi Zeira (third generation Palestinian Amora, end of third century) reports that the daughters of Israel themselves were so concerned about this matter that even were they to see only a drop of blood the size of a mustard seed they would wait seven clean days before immersing—an unnecessary stringency by any definition.

Still, this stringency came to be accepted as common practice, and today, therefore, a woman must wait seven clean days following her period regardless of when it occurs. The source of this practice, according to Maimonides, may be found ultimately in the artificial eighteen-day cycle. Had this eleven day period never been suggested then the law concerning menstruation would, as we have seen, maintain a condition of leniency for women.

Two sources of confusion …

Nachmanides, among others, has a very different understanding of the “eleven days …,” leading to another justification for the stringencies described at Niddah 66a.
According to Nachmanides (Laws of Niddah, ch. 1), the phrase “Eleven days between one Niddah and the next” must not be read literally as proposed by Maimonides. For Nachmanides, rather, the eleven days are a time during which a blood flow is considered as unnatural, but following which a blood flow is considered natural (that is: Niddah).

According to this approach, after a woman’s period, she must count eleven days. If she experiences an extended flow during this time, she becomes a zavah (one who has had an unnatural flow). But after that time, any flow is considered natural. A new Niddah period begins whenever, after the eleven days, new blood is sighted, whether on the twelfth day (the nineteenth day of her monthly cycle) or the twentieth (the twenty-seventh day of her monthly cycle). The result of this interpretation is, at least in theory, a leniency, and in this sense Nachmanides stands in sharp contrast to Maimonides.

Since only unnatural blood leads to the more severe degree of impurity, it is “better” to restrict, as much as possible, the possibility of considering a flow unnatural. By saying that only blood sighted within eleven days from the completion of the last period can be considered unnatural, the tradition is declaring that any other blood must be viewed as natural—a clear leniency in the law. This means that if a woman ordinarily has a twenty-eight-day cycle, even if she begins to sight blood on the twentieth day—which for her would be quite unnatural—the law will define this blood as Niddah blood and require of her only the less stringent demands made of a Niddah.

If for Nachmanides the “eleven days” is intended to be a leniency, whence the stringent direction that the law followed? Nachmanides explains that the stringencies associated with Rabbi Judah HaNasi and Zeira can be attributed to two possible sources of confusion: one a matter of counting and the other a matter of distinguishing different kinds of flows.

The fear of error in counting is this: a woman might sight blood on day eleven of the “eleven days” and mistakenly think that it is the twelfth day, the day on which her Niddah begins. She will begin counting the seven days of her Niddah too early and will consequently think that her Niddah has ended before it is actually over. Alternatively, it is possible that a woman counting the seven clean days required of her when she has become a zavah (having first seen unnatural blood for three consecutive days) will see some flow on the seventh day and mistakenly suppose that it is the eighth day. Since any sighting during the “seven clean days” necessitates that the counting begin anew, she will assume that she has just begun a new niddah, whereas in fact she remains a zavah. Obviously, if it is possible to confuse a zavah and a niddah, clean days must be required even of a niddah.

The fear of error in distinguishing flows is connected to the fact that not all kinds of blood or other secretions are considered impure (see Mishnah Niddah 2:6). Presumably, this is also intended to provide a leniency in the law. If all blood flows or secretions were considered impure, then many women would constantly be in a state of impurity, since many women experience different kinds of staining throughout their cycles. Restricting that which can be considered impure would protect women from this intolerable consequence.

But, in fact, the result of this “leniency” is quite the opposite. The problem is this: because we no longer have “experts” who can distinguish between pure and impure blood, a woman might sight blood for seven consecutive days and think that they are all to be counted as days of her Niddah. After this, of course, she will consider herself pure.

But what if the blood during the first six days was in fact “pure” blood, so that her Niddah actually only began on what she thought was day seven? Niddah would continue for seven days from what she thought was day seven, and as a result she would consider herself pure during what are actually the days of her niddah. Obviously, this is a situation that the Rabbis thought it proper to avoid.

Nachmanides’ interpretation avoids the discord between nature and tradition that is established by Maimonides. But the consequence is the need to attribute later stringencies to a variety of largely obscure fears. For Maimonides the source of these stringencies is obvious and necessary; for Nachmanides it requires defining the legal norm by cases that are presumably abnormal.

The Spirit of the Law

The effect of the laws as currently constituted is this: a man and wife may not enjoy sexual relations for fully one-half of the month, that is, for half of their married life. Alternative sources exhibit a contradictory spirit, however—one which values sexuality and which would likely not tolerate the Niddah law as presently defined.

The Mishnah in Ketuboth suggests the proper frequency of sexual relations, taking into account the requirements of different occupations (5:6).

The Six Orders of the Mishnah Wikipedia

According to its provisions, absence of sexual intimacy for fourteen days would be acceptable only for a husband who travels out of town. Otherwise it would be too long. When offering an explanation for the seven days of niddah (Niddah 31b) R. Meir says that abstention for a period of this duration will cause a woman, when she rejoins her husband in sexual relations, to be beloved to him as the day of their wedding. The same reason would, I suspect, be untenable if the period were extended to fourteen days. Finally, in a dispute (Ketuboth 5:6) concerning the length of time a husband who has sworn not to have sexual intercourse with his wife may remain married before he must give her a divorce, the School of Shammai describe a 14-day maximum, while the School of Hillel allows for a maximum period of abstention of only seven days (the length of her state of niddah). The longer duration would, according to Hillel, be offensive to the institution of marriage, and is therefore unacceptable. To express it otherwise, the School of Hillel could not permit the present practice of waiting fourteen days.

Searching for a Source

If, in light of the spirit described above, we consider the present situation to be untenable, we must consider what responses are available to each of the primary interpretations. For Maimonides, it is the eighteen-day cycle that creates our problems. How are we to understand its origin and authority?

The Sifra (midrash halakhah to Leviticus), which is quoted in the gemara, derived the eleven days through midrash (it does not discuss the alternative tradition that it is “halakhah to Moses from Sinai”). Yet, despite the midrash, Rashi recognizes that eleven days is not the simple meaning of the text, as reflected in his comment to Lev. 15, vs. 25. There he first describes the differ-ence between a menstruant and one who has had an unnatural issue as the Torah understood it, and only then continues by stating “and they expounded in this section the eleven days between the end of one period to the beginning of another period.”

This structural bifurcation reflects his opinion that the latter is not inherent in the text. We have seen, moreover, that for Maimonides the effect of the eleven days is in fact contradictory to the original intent of the text. These factors must lead us to question the origin of the midrash; it is surely not the Torah text itself that requires these conclusions. Rather, the midrash is most likely a “corroborating midrash” (according to the categories suggested by M. Elon in HaMishpat HaIvri)—one which seeks to justify through scripture a pre-existing law. If so, the alternative tradition, reported in the name of Rabbi Elazar hen Azariah. which describes the “eleven days” as “halakhah to Moses from Sinai” must be considered seriously. This proposed origin is also, however, not without its problems.

In order for a particular law to be considered halakhah le-Moshe mi-Sinai, Maimonides contends, it must not be derivable from scripture either by logic or by way of other midrashic devices (see his Introduction to the Mishnah). If this is true, then the eleven days cannot be halakhah le-Moshe mi-Sinai because, as the Sifra demonstrates, it can be based on a source in the Torah.

Even if we do not accept Maimonides’ definition (or if we think that the dispute is precisely whether the “eleven days” can be derived or not), the institution of “halakhah to Moses from Sinai” retains its inherent difficulties. A case in Mishnah Yadaim (4:3), for example, reflects that a law which is labeled “halakhah” is in fact a rabbinic injunction. Elsewhere (Shabbat 11a) a law which is accounted by R. Elazar as “halakhah” is praised by R. Ishmael in the statement “Great are the words of the sages.”

Aware of these and similar cases R. Asher suggests that the phrase “halakhah to Moses from Sinai” often refers to a law which is as clear as though it had been given to Moses at Sinai (Laws of Mikvah 1). Even the midrash (Menachot 29b) recognizes that Moses did not in fact receive the laws which possess this appellation, but nonetheless they are to be respected because they lend strength to the tradition. “Laws to Moses from Sinai” are typically either ancient traditions which have no basis in scripture (black, squared tefillin), or laws, sometimes rabbinic in origin, which might be difficult to accept without the authority of Moses’ name (tithing in Ammon and Moab). The eleven-day period, it would appear, falls into this latter category.

But again, if not midrashic in origin, whence the 11/18 days? Maimonides, we noted, suggests that eleven days is the very shortest time which might pass between one menstruation and the next. Regardless of the biological accuracy of this proposal (Our Bodies, Ourselves, by the Boston Women’s Health Book Collective, remarks [p. 18] that a normal cycle might range between 20–36 days) it is nonetheless valuable because it retains a “rational” origin for the Rabbinic cycle.

Yet considering the Torah’s appreciation of menstruation as a natural event, it is perplexing that the law should ultimately be defined by the abnormal extreme of the normal. If, on the other hand, Nachmanides’ interpretation is more likely, then response to its effects must be more a matter of judgment, not an analysis of legal systems and institutions. The fear for counting is, in the context of this interpretation, an ironic one.

The beauty of Nachmanides’ system in the first place is that it is so much more in accord with natural cycles—cycles which, presumably, a woman would have far less trouble counting. In this system, a woman would ordinarily have to count the seven days of her Niddah, followed by eleven until she again sighted blood, generally at the beginning of her next period. She would rarely sight blood during her “eleven days”—unlike the Maimonides’ system where her period would by definition frequently fall within her “eleven days”—and so both of the situations of confusion described above would be very unlikely events. This is not to say that they would never occur, but halakha has never been intolerant of errors of this sort, and it certainly does not define itself in anticipation that they might occur. Quite the contrary, from the Torah forward provision has always been made for atoning for just this kind of error. Why should the realm of sexual purity be different?

The matter of being unable to distinguish pure blood from impure blood is more difficult. Here we must be left, again, only to notice the irony. The fear that Nachmanides expresses is that pure blood might mistakenly be considered impure. The result of this mistaken “stringency” would be a tragic “leniency,” in that her Niddah should actually begin later than she began counting it.

But the point of defining some secretions as being pure was to lend leniency to a condition that might otherwise be intolerable for some women. Has this grant to some women led to an intolerable situation for all women? Would it not be better, in fact, to allow for the possibility that a rare mistake might be made rather than penalizing all women because of this fear? As we have noted, the law is amply prepared to handle such errors.

The study of niddah is incomplete while the mystery of the origin of the “eleven days” and its related consequences remains unsolved. It represents, nonetheless, a striking example of halakhic development which has been significantly influenced by popular fears (the blood tabu—remember Rabbi Zeira’s report of the “daughters of Israel”). Cultural anthropologists have confirmed the power of this fear in many a “primitive” society—a power which persisted and prevailed in Jewish society despite the contradictory instruction of Torah. Perhaps, having been released from these tabus by the enlightening influence of modern science, we might finally permit the tolerant preference of the Torah (which requires no clean days following menstruation) to gain ascendance.

Modern responsa on the laws of family purity, from the Committee on Jewish Law and Standards (CJLS)

Mikveh and the sanctity of being created human, Rabbi Susan Grossman

Observing Niddah in our Day, Rabbi Avram Israel Reisner

Reshaping the laws of family purity, Rabbi Miriam Berkowitz

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