Many people are familiar with the term mikvah, fewer are familiar with the term niddah, and still fewer know about Family Purity Laws in Judaism.
Family Purity Laws
The Laws of Family Purity, as recorded in the Torah (Lev. 15:19-24), prohibit a husband from having intercourse with a menstruating woman. Family Purity Laws, called Taharat Ha-Mishpachah in Hebrew, are also referred to as the Jewish Laws of Separation.
Talmudic scholars extended the period of separation so that it lasts a minimum of 12 days. Separation begins at the first sign of blood. According to Jewish Law, the minimum period of menstrual flow is five days. Separation ends in the evening of the woman's seventh "clean day."
In addition, the rabbis broadened the Law's definition of separation. Whereas the Bible prohibits intercourse, the rabbis decided that a man should not share a bed or even touch his wife while she is ritually impure.
Niddah refers to a woman who is ritually impure. She is considered ritually impure while she is menstruating and for seven post-menstrual days. According to the Family Purity Laws, as soon as possible after nightfall of the seventh post-menstrual "clean" day, the woman must immerse herself in a mikvah. After she has purified herself in the mikvah, then she can resume sexual relations with her husband.
A mikvah (also pronounced mikveh) is a ritual bath. The purpose of the mikvah is solely ritual purification, not physical cleanliness. One must thoroughly bathe before entering into and being purified by a mikvah.
A Mikveh may be either stationary rain water or flowing well/spring water. Oceans, lakes, ponds and springs are all natural catch basins of rainwater, and thus can be used as mikvaot (plural for mikvah). This body of water must contain at least 480 liters of water that has not been drawn or stored in a vessel (Lev: 11:36). Most mikvaot today, which exist in cities, use 480 liters of undrawn water (channeled rainwater or melted snow), and then add water pumped from a faucet to reach a depth comfortable for immersion.
Mikvaot are primarily used by post-menstruant women and by converts to Judaism. Some orthodox Jewish men will immerse themselves in the mikvah before the Sabbath or a holiday.
The prevalence of mikvaot in Jewish communities, both in Israel and in the Diaspora, from the time of the Second Temple until today, shows how important Family Purity Laws have been to the Jews throughout their history. Today, however, the great majority of non-orthodox Jews, which makes up the great majority of Jews in general, do not observe or even understand Judaism's Family Purity Laws.
Most of the Jews who know about and observe a period of sexual abstention do so because it is a commandment from the Torah. There are others, however, who practice Judaism's Family Purity Laws because they see both physical and psychological benefits from observing a period of separation.
Two weeks after a woman has begun to menstruate, she is most fertile and likely to conceive. At the same time, a man who has abstained from sex for two weeks will have an increased sperm count. Thus, observing this period of separation can increase the likelihood of conception. Secondly, it is believed that women who have sexual intercourse while menstrating are more vulnerable to a variety of vaginal infections and even cervical cancer.
Many believe that this period of separation also has psychological benefits. A couple that abstains from sex for two weeks each month is likely over time to form a strong non-physical attachment to each other. Over time and especially as the couple ages, this non-physical bond becomes an important part of a marriage. Secondly, like anything that isn't constantly available, the physical relationship between the husband and wife becomes more special and appreciated as a result of this period of physical separation.