ויקרא, פרק ט״ו, פסוק ט״ז

A seminal emission is a natural physical event, yet it carries deep spiritual weight. It rests on the delicate boundary between the powerful force of life creation and the loss of that very potential, bringing about a temporary state of impurity. The laws governing this state apply specifically to a male who has reached a baseline of physical maturity, defined as nine years and one day, rendering him theoretically capable of fathering a child [תורה תמימה, רלב״ג, חזקוני, אדרת אליהו]. The impurity takes effect only when the fluid physically exits the body [תורה תמימה, חזקוני, אדרת אליהו], an event that frequently occurs involuntarily [אבן עזרא, אבי עזר, רד״צ הופמן]. The action is characterized by a pouring or spreading outward, much like the settling of morning dew [שד״ל, אבן עזרא, רד״צ הופמן]. To trigger the state of impurity, the fluid must retain its natural texture, be fit for fertilization, and exit with force [רלב״ג, הכתב והקבלה, אדרת אליהו].

While some commentators associate this impurity exclusively with the physical act of union [אם למקרא], a broader question arises: why does a natural bodily function tied to human reproduction result in impurity at all? The primary approach among commentators draws a parallel to the impurity imparted by a human corpse. When reproductive fluid is released without fulfilling its ultimate purpose of creating a child, a profound loss of potential occurs. This unfulfilled potential resembles a localized loss of life [רמב״ן מובא בשפתי כהן ובפרדס יוסף]. Furthermore, particularly when an emission occurs at night, it frequently stems from wandering thoughts and a mixture of physical urges and desires. This reality necessitates a period of spiritual reflection and purification [שפתי כהן]. Ultimately, this impurity is not a matter of physical hygiene or adjusting to the climate, but a deep spiritual decree designed to cleanse the soul [אם למקרא].

The path back to purity requires a precise process of immersion. This cannot be accomplished with standard drawn water; it requires natural, gathered water, known as a mikveh [תורה תמימה, רש״ר הירש, רד״צ הופמן]. The individual must submerge his entire body simultaneously, ensuring absolutely nothing blocks the direct contact between his flesh and the water. This strict requirement extends to the hair, which must also interact naturally and completely with the water [תורה תמימה, רש״ר הירש, רד״צ הופמן, אדרת אליהו]. These parameters dictate the physical dimensions of the mikveh itself, requiring enough volume to completely encompass a human body—a measurement established by the sages as forty units of water [ביאור יש״ר, העמק דבר, חזקוני, רד״צ הופמן].

Commentators offer different perspectives on why immersing the entire body is so heavily emphasized for this specific situation. One explanation suggests that during a nocturnal emission, the physical elements of the body lie dormant while only the inner spirit and desires remain active. This dynamic renders the physical emission akin to lifeless flesh, thereby requiring the entire body to undergo a thorough purification [רבנו בחיי]. Another perspective views this emphasis as a necessary safeguard against a logical error. Without it, a person might assume that merely washing the reproductive organ would suffice. By establishing the absolute requirement for full-body immersion in this relatively minor case, the standard is firmly set for all other, more severe forms of impurity [רד״צ הופמן]. Because this impurity stems from a natural bodily function rather than an illness, it remains a mild state. Following immersion, the individual waits only until evening; as the sun sets, he is rendered completely pure and may freely return to the camp [ביאור שטיינזלץ, רד״צ הופמן].