The halakhot of niddah are equally complex and important. They deal with the laws of "menstruous woman"). According to Jewish law, a woman is forbidden to maintain sexual relations with her husband during and for some time both before and after her menses. The laws relating to the menstruous woman comprise some of the most fundamental principles of the halakhic system, while a scrupulous observance of their minutiae has been one of the distinguishing signs of an exemplary traditional Jewish family life. Among the most difficult and intricate in the entire range of the halakhah, these laws are elucidated in a lengthy and detailed tractate of the same name devoted to the subject (see Niddah, tractate). The historical development of the relevant halakhot through the centuries is likewise extremely complicated. To decide a law relating to a menstruous woman demands, besides a profound knowledge of the halakhah, experience in various medical matters, and at times also the ability to assume the grave responsibility of disqualifying a woman from pursuing a normal married life and of—at times—separating her forever from her husband. In every generation and in every place there have generally been men, referred to in the Talmud simply as "sages," who specialized in the subject, as did eminent tannaim and amoraim, to whom particularly difficult questions were sent, even from remote places, together with specimens of blood (Nid. 20b). In brief, the halakhah as at present codified is that sexual intercourse (and any other intimacies which may lead to it) is forbidden from the time the woman expects her menses until seven clean days (i.e., days on which no blood whatsoever is seen) have elapsed. For this purpose a minimum of five days is fixed for the menses themselves. Thus the minimum period of separation is 12 days. In the evening of the seventh day without sign of blood the woman immerses herself in a mikveh and normal marital relations are resumed until the next menses are expected. Any bleeding is considered as menstrual and requires a waiting period of seven clean days. The laws of niddah are codified in the Shulhan Arukh, Yoreh De'ah, 183–200.

דף [2]: מבוא הפרדס, מאת ר' אברהם שמואל, בן המחבר, שהביא את הספר לדפוס.