ויקרא, פרק ט״ו, פסוק י״ט

Menstruation is a natural phenomenon woven into the human life cycle, fundamentally distinct from abnormal diseases or unusual physical discharges [ביאור יש״ר, ביאור שטיינזלץ, שפתי כהן]. The roots of this physical reality reach back to the dawn of human history, serving as a consequence and constant reminder of the sin of the Tree of Knowledge and the curse of Eve [ספורנו, תולדות יצחק, שפתי כהן, חומש קה״ת]. Yet, alongside this historical reminder, there is a profound biological and spiritual benefit. By cleansing the body of residues, the process ensures that future offspring will be formed from pure, clean blood. This physical preparation readies the child spiritually to receive Divine abundance and intellectual light [רבינו בחיי, תולדות יצחק, שפתי כהן].

These laws apply universally to all females, even to a one-day-old infant [תורה תמימה, אדרת אליהו, רלב״ג]. The ritual impurity is triggered exclusively by red blood, or similar dark shades like black and earth tones, whereas white discharges do not have this effect [רש״י, רשב״ם, רבינו בחיי, רלב״ג, אדרת אליהו]. The impurity takes hold only when the blood originates from its internal source within the reproductive organs, rather than from any other bleeding in the body [אבן עזרא, חזקוני, פירושי רד צ הופמן, רש״י, מזרחי, תורה תמימה]. The process begins the very moment the blood is displaced and enters the internal birth canal, even before it physically exits the body [תורה תמימה, בכור שור, אדרת אליהו]. Furthermore, unlike the laws governing male impurities, a woman enters this state even if the bleeding is triggered by an accident or an unexpected external factor [רלב״ג, בכור שור, פירושי רד צ הופמן].

A strict, continuous period of seven days and nights is established for this state [תורה תמימה, אדרת אליהו]. The primary approach among commentators is that this duration is absolute and does not depend on the amount of bleeding. Whether a woman experiences a single drop on the first day or bleeds continuously, she remains in this state for a full seven days. This fixed timeframe provides a period of rest, allowing a woman who has been physically weakened to fully regain her strength and health [תורה תמימה]. Additionally, this temporary physical distance creates a natural renewal within marriage, ensuring that a wife remains as beloved and desirable to her husband as she was on their wedding day [תורה תמימה].

The very concept of this state is rooted in ideas of wandering, distance, and isolation, as the woman is separated from physical contact with others during this time [רש״י, משכיל לדוד, ביאור יש״ר]. Anyone who touches her becomes ritually impure until the evening. Because direct contact transfers this status, it naturally follows that the utensils, clothing, and furniture she uses or sits upon also absorb and transmit the impurity [העמק דבר, פירושי רד צ הופמן]. Because the seven-day period must be entirely complete, she cannot immerse in a ritual bath during the seventh day itself; she must wait until nightfall to achieve purity [רבינו בחיי, רלב״ג, חזקוני, אדרת אליהו, רש ר הירש]. Later in history, Israelite women adopted a stricter practice, choosing to wait seven completely clean days without any bleeding, even if they initially experienced only a single drop [בכור שור, חומש קה״ת].