Science in the Torah

The Physiological Stages of the Monthly Cycle

Among the most fundamental Jewish commandments are the Family Purity Laws. This means that after four (and some say five) days from the time a woman received her monthly cycle until the woman has made certain by checking herself that she is completely clean, the woman then counts seven more “clean” days after which she immerses herself in a mikvah (a pool of clear water built according to certain legal specifications which gives it its status as “a purifying mikvah” — sometimes translated as a ritual bath). From the onset of her cycle until after she immerses herself in the mikvah, a couple are forbidden to have any physical contact with each other. (This extremely grave prohibition is called in the Jewish legal literature “the prohibition of Nidah” and it also applies to unmarried men and women. This is in addition to the prohibition of touching any woman (besides close relatives) including even one who is not a Nidah, outside of the framework of marriage.)

This law which superficially appears rather bizarre to an average person, was shown by modern scientists to have been based on profound knowledge of the physiological structure of the human reproductive organs, and the biological laws by which those organs function. This knowledge must have encompassed and taken into consideration numerous unknown details of the exact time when changes occurs to those organs — details that were only discovered by scientists in the last generation and only through modern scientific devices.

Not only that, it is clear that this wonderful law gives a suitable solution to a number of severe medical and social problems that many married couples suffer from. This shows that beyond the above, this law was composed by an expert in human health and medicine, who possessed knowledge of psychology, hormones, physiology and biology, as well as the social need for intimacy.


To clearly understand the topic, we will use passages from an article by Dr. Eli Schussheim “Health and Happiness in Marriage” (with additional explanations and emphases added):

From the point of view of chronology, there is an amazingly exact coordination between Jewish tradition and medical science concerning the three stages or periods that physiologically divide a woman’s monthly cycle.

First we will start with the first two stages, and then we’ll go on to the third stage.


In the first stage — the mucus membrane that coats the interior of the womb breaks up and disintegrates and causes bleeding. In the second stage, the womb rebuilds the destroyed membrane to prepare it to receive and nourish a developing fetus.

Modern scientific devices have discovered that the new membrane takes 7 days to form from the end of the discharge. Scientists were amazed to discover that according to Jewish law, after the discharge finishes, a woman has to wait seven days in which she is clean, and only then may she immerse herself in a mikvah and resume relations with her husband.


Before we mention another interesting detail on this, we must emphasize that the Torah’s commandments were not given for mere health reasons, but are “king’s orders” which are based on many unfathomable reasons and rationales, and we have to keep them whether or not we realize their health benefit or any other benefit. Nevertheless, it is obvious to us that the Creator of the world Who is also the Creator of Nature, did not issue any commandment that would cause damage to our health. To the contrary, His commandments mandating the actions we should do, the foods we should eat etc. were clearly meant to preserve our health and contribute to our welfare. Nevertheless, we should always remember that this is not the reason and purpose of the commandment, but their inevitable outcome.

After clarifying this perspective, we note that parallel to the above finding that the womb mucus membrane takes seven days to be reconstructed, it turns out that as long as the membrane was not completed, the interior is like a sponge that absorbs external viruses, and serves as a convenient breeding grounds for virus colonies that can cause terrible diseases. By a couple keeping separate during these days, they are saved this serious risk.

Experts say that “In recent times, a couple’s failure to keeps intimate relations according to Jewish law, as well as the permissiveness that is rife in our period, explains why Jewish women have lost their known natural “immunization” from cancer of the womb and why it has become common.”


We can go into more detail about the ramifications of this wonderful commandment, from which we can definitely prove what our forefathers always knew, that G-d Who created mankind and the universe, is the One Who wrote the Torah. We will just bring here two short additional findings, and rely on the intelligence of our readers to reflect on them, expand their mind and reach the obvious conclusions.

1. We mentioned above the two first stages, the break-up of the mucus membrane and its reconstruction. As we stated above, the Torah was well informed about the length of these stages. In the third stage, ovulation occurs. This means that the egg that is ready to develop into a fetus leaves the ovaries. Ovulation takes place as soon as the mucus membrane was rebuilt (to absorb the developing fetus and nourish it). Advanced scanners allow us to see this development in large scale. The astonishing significance is that the day when a woman immerses herself in a mikvah according to the Torah, which is when the husband has a commandment to have relations with his wife, is the day best suited for absorbing the fetus!!
What is especially interesting is the convergence between the date when the immersion is mandated — after a woman finishes counting 7 clean days — and the time when she is most likely to become pregnant, i.e. the time of ovulation after the membrane was rebuilt over 7 days, was not recently discovered based on the above biological findings but were clearly said and defined in the Oral Tradition in this following short sentence: “A woman will only become pregnant close to her immersion” etc. (Niddah 31b. See also Midrash Rabbah Vayikra 14:5: “a woman only absorbs the fertilized egg after [she concluded] being a Niddah.”)

2. The Talmud says: “Why does the Torah say she should be a Niddah for 7 days? Because if he will have her always available, he will become disgusted of her (Rashi: he will be repulsed by her). The Torah says it is better that she be forbidden to him 7 days so that she will be beloved to her husband as when they were wed.” (Niddah 30b). This saying, which comes to illuminate the family purity laws from the angle of a healthy, ongoing relationship between the couple, sums up for us the ideal and wonderful solution to the ultimate problem in a modern marital relationship — a couple’s boredom, aversion, and distancing from each other, until the home is utterly destroyed. There is much to say on this, but we will let the reader reflect on this himself.


Before we finish, it is necessary to again emphasize that any parallel to research studies and any of the additional wonderful advantages which we gain from this commandment and other commandments, are like ornaments and flowers which adorn the commandment. They are an inevitable part that accompanies it due to its being given by the Creator of the universe. But their essence is far more sublime and exalted than any benefits which researchers may come up with.

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