Why are there boundaries for sexuality?
If there is anything more personal than kashrut, this has to be it: sexuality. And as with kashrut, so here, part of the core of the issue is one of relational boundaries: are we going to accord God the right to "intrude" into our sex lives? To the extent that we consider God's prescriptions on this matter intrusive, we demonstrate our failure to understand that sex is God's gift to us, not our own creation, that we are God's servants in every area of life, and that God therefore has every right to make the rules.
This doesn't go down well in our generation. Not only is our culture oversexed and overstimulated, we have converted the entire domain of sexuality to a matter of individual rights and preferences. Once the issues are thus described, any input from God can only be viewed as "another opinion." But this will not do.
Two errors must be avoided in seeking to honor God in matters of niddah. First, the "impurity" (tumah) that attaches to a menstruant woman, or to a man who has ejaculated for that matter, has nothing to do with "dirtiness." In the days of our ancestors, this impurity indicated that such a person was temporarily separated from normal access to the Tabernacle or Temple. This is generally interpreted to mean that when a woman menstruates or a man ejaculates, we draw near to the mystery of the creation of life itself - and this is so special, that such an encounter immediately puts the persons involved into a temporary special category. They are set aside, not as discarded or rejected, but in respect for the holy otherness of what has just occurred.
Niddah is all about respect for sexuality, for procreation, for the mystery of life and our privilege to have such an intimate connection to its creation.
The second error is to view niddah as a form of deprivation. In reality, it is a matter of protection. The constraints of niddah protect the sanctity of sexual relations, elevating our awareness that sex is a gift to be enjoyed, and never taken for granted.
Sexuality is so powerful that it can easily control a person, and all of us know people whose sex drives drive them. This should not be. Sex is a gift from God to be enjoyed, full of developing delights, not something that controls and drives us, depriving us of freedom. When sexuality is fully expressed within its rightful boundaries, marital joy remains conscious, full, and unsullied.
God's word about sex therefore is a familiar one: Enjoy! But the only way this can happen is to respect the limits God has set, ever mindful that sexual union is a gift, not a personal right. Niddah is a gift from God, given that we might enjoy marital sex, mindful that it too is a gift from God.
Decision & Commentary
According to our basic practice, all sexual relations should be avoided for a full seven days from the onset of the woman's monthly menstrual period, or until the menstrual period has ended, whichever is longer.
The Torah explicitly forbids all sexual relations during a woman's menstrual period (Leviticus 18:19; 20:18). It also determines that a menstruant is to be considered ritually impure (and thus sexually inactive) for seven days from the onset of menstruation (Leviticus 15:19). Thus, our basic practice adheres to the straightforward meaning (peshat) of the biblical text.
After dealing with the normal menstrual period (Leviticus 15:19-24), the Torah proceeds to discuss the woman with an extended abnormal discharge (Leviticus 15:25-30). In such cases, the purification process requires seven days from the time the discharge ends (Leviticus 15:28). Jewish tradition combined this latter ruling with the previous unit concerning menstruation, and determined that a normal menstruant must wait seven full days after the cessation of her period (or after five days from the onset of menstruation, if her period lasted less than five days), and then immerse herself in a mikveh. She may then resume having sexual relations with her husband.
We view this traditional practice as a commendable fence around the Torah, to be treated with respect. Nevertheless, our basic practice is limited to the requirements contained in the peshat of the biblical law.