The attempt to place this bomb delicately was doomed to failure from the start. Those who planted it a month ago, in an article in the national religious newspaper Hatzofeh, knew very well how volatile it was. Not only did it raise fundamental questions about halakha and the authority of Orthodox rabbis, but it addressed issues that are usually covered by a heavy, impermeable cloak of silence: the intimate sides of family life, infertility, marital tensions and more. The explosion was to be expected, as were the shock waves and the return fire. On the Internet, they were labeled in antique terms: "those who cause many to sin," "your destroyers and those who laid you waste" and more.

It began with an interview Hatzofeh published in early November with a religiously observant gynecologist, Dr. Daniel Rosenak. On religious and medical grounds, he called for "rethinking" the rules of niddah, which pertain to menstrual impurity and are considered among the most important of Jewish religious injunctions. Put plainly, Rosenak called for changing a 1,500-year-old religious practice, thereby cutting a couple's monthly period of sexual abstinence by half, from two weeks to one.

To secular ears this might sound trivial, even absurd. For the religiously observant, however, it represented an extreme, revolutionary suggestion printed in a newspaper of the conservative establishment. The guest interviewer at Hatzofeh was Rivka Shimon, a brides counselor who supports Rosenak's position. The interview provoked hundreds of responses - articles, letters to the editor and online discussions.. Some were excited, others irate.

Although Rosenak repeatedly emphasized that he did not presume to give a religious ruling, the language and the arguments he used were completely rooted in halakha. He had clearly researched dozens of religious and historical sources dealing with the law of niddah before the interview, and he reviewed them in the paper. He is not proposing an easing of religious obligations, he said, but rather meticulous observance in order to avoid "distortions" of other religious laws.

In the interview, Rosenak said that many religious people were not aware of the source of the law of niddah. The biblical book of Leviticus (chapter 15) contains several laws regarding purity and impurity. One relates to niddah (menstruation) and another to ziva (secretion or discharge of blood unconnected to the menstrual cycle). Niddah continues for a defined period of seven days, counted from the first day of menstruation. On the eighth day, the woman must immerse herself in a ritual bath, thus ending the time of abstinence. Regarding ziva, the additional seven days are only counted from the complete disappearance of the discharge, and are followed by immersion.

At some point, the religious practice was made more rigorous, and sages began to relate to niddah as to ziva. Instead of seven days, the monthly period of abstinence continued for two weeks. Only after the menstrual period of five to seven days would the woman begin counting the seven "clean" days, and immerse herself on the eighth.

Rosenak quotes "halakhic" precedents, which suggest that because the added severity of a religious practice derives from custom, rather than law, it may be easier for contemporary rabbis to reverse it. His main argument is that Rabbi Zeira's rigorous ruling created "problems" and "distortions," especially relating to what is called "halakhic infertility."

In the interview, Rosenak said, "Through my work as a gynecologist, especially in the ultra-Orthodox and national religious communities, it transpires that more than one quarter of the infertility cases result from what is called 'halakhic infertility.' That means that tens of thousands of women go to the mikveh when their period of ovulation is past." According to Rosenak, the chance of fictitious infertility contradicts other laws, foremost among them the law to "be fruitful and multiply."

Behind the ignorance described in the article lies the human tragedy of couples who are unaware that what prevents them from having children is "halakhic infertility." On Hatzofeh's Web site, someone posted the following response to the interview: "I don't believe it," wrote a reader who identified herself as Rivka. "After years of such suffering, when I couldn't get pregnant, and remained cut off from the world, it suddenly turns out that it is all because of a rabbinic ruling? Have you gone mad? You destroyed my life because of a rabbinic ruling? Do you have G-d in your hearts???!!!!!!"

Even if the response was not authentic, Haaretz met a woman in a settlement south of Jerusalem who for years had tried to get pregnant. She discovered recently that what prevented a pregnancy was "halakhic infertility." Now 48, she is trying to conceive with donor eggs.

"I haven't come to change things," says Rosenak. "I want to expose the problems of this custom, and bring the issue into the open. The public must know that this is not a biblical commandment but a custom that has taken root, a custom that is the source of many problems."

Here lies the article's theological time-bomb: From an Orthodox perspective, a demand for "rethinking" a religious law implies rethinking a fundamental tenet of the faith according to which the words of the ancient sages are "living words of G-d," and challenging the iron rule that the sages' rulings are not to be changed.

Over the last few weeks, Hatzofeh published a series of articles in response. Rabbi Benny Lau, one of the more liberal rabbis in the religious Zionist camp, wrote an article, together with his wife Noa, taking issue with Rosenak. "Humra (a severe ruling) carries the authority of law," they wrote. "This is a humra that became law in the days of the sages, when the halakha was being formulated, and was accepted by all the authorities, from the Amoraim [Talmudic sages] onward." They also wrote that there are medical solutions to the problem of halakhic infertility, hormones that delay ovulation until after the woman's immersion.

Rosenak related to this in his follow-up article last week, writing that shifting the solution from the sphere of halakha to the sphere of medicine is "an interesting argument." "Halakhic infertility is not a medical problem ... It is a purely halakhic problem, and its solution has to be halakhic, not medical." Criticizing the Laus' contention that "it is hard to assume that hormones will seriously harm the woman's body," Rosenak calls it "an irresponsible statement that requires scientific proof" and "grave."

"These are matters of life and death!" he wrote. "I tremble every time I am forced to prescribe hormones for a woman who has no genuine medical problem. Perhaps the woman sitting opposite me has an undiscovered genetic predisposition to breast cancer? Perhaps, heaven forbid, she could have a stroke?"

It is no coincidence that the call to abrogate "the severe ruling of Rabbi Zeira" comes from a man who is not a rabbi. In its wider context, it comes from a quiet and unorganized grass-roots movement that challenges the establishment and the rabbis. Alongside ultra-Orthodox tendencies in religious Zionist circles, and the increasingly strict interpretation of religious practice and obedience to rabbis in yeshivot like Mercaz Harav, a not-insignificant segment of the religious population is demanding changes in the religious way of life and religious norms.

An earlier grass-roots campaign - women studying Torah - is considered a revolution today. It started with groups of women who began learning Gemara [Talmud] without waiting for permission from rabbis who saw it as "breaching fences." In recent years, the phenomenon has slowly spread to the mainstream, to the extent that rabbis can no longer ignore it, and some have yielded. Today, even the Conservative wing has colleges and high schools where women and girls learn Gemara. The ultra-Orthodox community has its own quiet revolutions, which its rabbis are increasingly accepting - like opening colleges for professional training, and branches of universities where women and men can acquire an academic education. Rosenak apparently wants to initiate a similar move in a purely halakhic matter.

Correcting a distortion Dr. Daniel Rosenak declined to be interviewed for this article. He knows that cooperation with Haaretz on such a sensitive subject would provide ammunition for his opponents, and would "damage the cause." He agreed, nevertheless, to release the following statement:

"The article was not intended to challenge halakha, nor to create a new version of Judaism, like Karaism or Reform. My article was intended to indicate a distortion that has been created as a result of a custom that over a long period has become a law. The humra of Jewish women having to count seven clean days for niddah, and not just for ziva as prescribed in the Torah, was accepted from earliest times as a law from which there is no deviation. Today we know that this ruling produces a problem of halakhic infertility in many women. Within this situation is a failure of internal logic: It is unreasonable that a ruling that derives from a humra of Jewish women will produce a conflict with the first commandment in the Torah - to be fruitful and multiply.

"The approach of many rabbis to 'treat' halakhic infertility with hormones, in order to delay ovulation, constitutes not only a medical problem (since the safety of the treatment - which increases chances of cancer and blood clots - has yet to be established), but also a halakhic problem of 'For your own sake, therefore, be most careful' (Deut. 4:15). Beyond that there is a problem of Jewish values. It is known that a doctor has a mandate to heal, and nothing else. He does not have a mandate to 'repair' what does not need to be repaired.

"The Torah gave human beings the power to do things, and to take stock constantly in the light of changing reality. The question is whether the change will come from the general public or will be initiated by courageous religious leaders ... It is my hope that raising the subject will contribute to restoring the purity of the Jewish home in the population at large, as an additional bridge toward national unity."