Chapter on Menstruation
Introduction
In Arabic one says: ḥāḍat al-marʾah, taḥīḍu ḥayḍan wa-maḥīḍan—“the woman menstruated; she is menstruating”—and she is described as ḥāʾiḍ when the blood flows. The feminine tāʾ marbūṭah is normally added to adjectives to distinguish masculine from feminine, yet with attributes that apply exclusively to women it is attached only when there is transmitted precedent; hence it is not said ḥāʾiḍah but ḥāʾiḍ.

Linguistically, ḥayḍ (menstruation) denotes “flowing,” as in their saying ḥāḍa al-wādī, “the valley overflowed.”

In the technical usage of the Law it is defined as: a natural, innate blood that the womb releases, habitually afflicting an adult woman at known intervals.

Medical analysis of menstruation states that the menstrual cycle lasts twenty-eight days. Day one is the first day of bleeding. By the fifth day, when the bleeding stops, tiny follicles begin to grow under the stimulation of hormones released from the pituitary gland inside the brain. Around the fourteenth day the uterus has prepared itself to receive a fertilised ovum. The level of the initial hormones then falls and is replaced by another hormone known as al-jaʿrūn. The concentration of this hormone rises and remains high if pregnancy occurs; it drops, however, if no pregnancy takes place. Blood then seeps inside the uterus and menstruation occurs. If conception does happen, no menstruation takes place.

The evidentiary basis for the rulings on menstruation rests upon the Quran, the Sunnah, and the consensus of the scholars: