הלכות מטמאי משכב ומושב

There are four women who are impure only from the time they discover uterine bleeding onward. They do not impart impurity retroactively. They are: a woman who is pregnant, one who is nursing, a maiden, or one who is elderly.
What is meant by a pregnant woman? A woman whose pregnancy has become obvious. If she was considered as pregnant and then experienced uterine bleeding and discharged a sack full of air or an entity that is not considered as a fetus, her status continues without and she is impure only from the time she discovers uterine bleeding onward. If she experienced uterine bleeding and directly afterwards, her pregnancy became obvious, she becomes impure retroactively like other women.
What is meant by a woman who is nursing? A woman within 24 months of childbirth, even if her child died within this time, she weaned him, or gave him to a nursemaid, she is impure only from the time bleeding is discovered. After 24 months, even if she continues to nurse, she becomes impure retroactively like other women.
What is meant by the term "a maiden"? A girl who has never menstruated, i.e., the intent is a maiden with regard to menstruation and not a maiden with regard to hymeneal bleeding. What is implied? Even if she was married and experienced uterine bleeding because of marriage or she gave birth and experienced uterine bleeding because of birth, she is still considered as a maiden with regard to the ruling that she is impure only from the time she discovers uterine bleeding onward.
What is meant by the term "elderly woman"? A woman who did not menstruate for three months as she approached advanced age. When is she considered elderly? When she is called an old woman by others in her presence and she does not protest. If three 30-day intervals pass and then she menstruates, another three 30-day intervals or more or less pass, and she menstruates, she is considered like other women and imparts impurity retroactively.

When a girl menstruates for the first time, even if her blood is flowing or dripping for all seven days, it is considered as if she experienced bleeding once. If she experienced bleeding, it stopped and then started again, it is considered as if she experienced bleeding twice.

When a young girl who had not yet reached the age when she is expected to menstruate experiences uterine bleeding for the first and second times, she is impure only from the time she discovers uterine bleeding onward. If she experiences bleeding a third time, she imparts impurity retroactively. If three months then pass without her menstruating and then she menstruates, she is impure only from the time she discovers uterine bleeding onward. If three other months then pass without her menstruating and then she menstruates, she is impure only from the time she discovers uterine bleeding onward. If three other months then pass without her menstruating and then she menstruates, she is impure retroactively.

When a young girl reaches the age when she can be expected to menstruate and experiences uterine bleeding for the first time, she is impure only from the time she discovers uterine bleeding onward. From the second occasion onward, she imparts impurity retroactively. If three months then pass without her menstruating and then she menstruates, she is impure only from the time she discovers uterine bleeding onward. If three other months then pass without her menstruating and then she menstruates, she is impure retroactively.

If a pregnant woman, one who is nursing or elderly, or a girl who has never menstruated, but has reached the age when that is likely experiences uterine bleeding once, she is impure only from the time she discovers uterine bleeding onward. If such a woman experiences bleeding a second time, she imparts impurity retroactively like all other women, as explained. If, however, the first time she experienced bleeding, it came because of external factors, she is impure only from the time she discovers uterine bleeding onward, even if she experiences bleeding a second time.

When a pregnant or nursing woman experienced uterine bleeding and then a three month interval passed before she experienced bleeding again, she is impure only from the time she discovers uterine bleeding onward. If another three months pass without her menstruating and then she experiences uterine bleeding again, i.e., a third experience of bleeding when counting the first, she imparts impurity retroactively.
When a woman experiences uterine bleeding within 24 hours of experiencing "the bleeding of purity," she is impure only from the time she discovers uterine bleeding onward.
Any woman about whom it is said, "she is impure only from the time she discovers uterine bleeding onward," must continuously inspect herself even though she does not impart impurity retroactively. All women who inspect themselves frequently are praiseworthy, with the exception of a woman in the nidah state and a woman who is granted "the bleeding of purity," for whom the inspections are of no consequence whatsoever.

The Sages ordained that Jewish women should inspect themselves every day in the morning because of the pure articles that they touched the previous evening and in the evening, because of the pure articles they touched in the morning. Whenever a woman partakes of terumah, she should inspect herself when she partakes of the terumah.
Every woman should inspect herself before she is intimate with her husband, because she also inspects herself for the sake of pure articles. If, however, she does not have to do with pure articles, she need not inspect herself for the sake of intimacy with her husband. For every woman who has a fixed time when she is expected to menstruate can operate on the presumption that at other times, she is pure with regard to relations with her husband, as we explained with regard to the laws of nidah.

Any garments stained with blood coming from Jewish homes are assumed to be impure. Those coming from gentile homes are considered to be pure. Those found in Jewish cities are considered to be pure. For Jews are not suspected of casting away their bloodstained garments. Instead, they are hidden away.
Accordingly, any bloodstained garments that are discovered are considered as pure with the exception of those in holes and around an impure room. In all instances, the impurity is only a decree, imposed because of doubt, as we explained.

Whenever a bloodstained garment is found, it should be treated with seven detergent agents. Afterwards, whether or not the stain is purged, the garment is immersed in a mikveh and then is deemed pure.
The rationale is that if it is not purged at all, it was a tint. If it was purged or its color faded, it is assumed to be a bloodstain. Since it was treated with these seven detergents, the blood has already been nullified even though a trace of it is still apparent. Even when a stain definitely came from nidah bleeding, once it was treated with these seven detergent agents, the blood is considered as nullified. The garment may be immersed and then used in connection with ritually pure entities.

When a bloodstain on a garment is no longer detectable, the entire garment should be treated with the seven detergent agents and then immersed.
The following laws apply when semen is no longer detectable on a garment: If it the garment was new, it should be checked with a needle. If the garment was worn, it should be inspected in the sun.

The following laws apply when a garment that was stained was immersed in the mikveh and then brought into contact with ritually pure articles. If afterwards it was treated with the seven detergent agents and was not purged, it is a tint. The ritually pure articles with which it came into contact remain ritually pure and there is no need to immerse it again. If the stain was purged or faded, it is a bloodstain. The pure articles are impure, because the person was concerned with the stain as evidenced by his removal of it. The garment must be immersed a second time to purify it.

When a stain was treated with six of the seven detergent agents and it was not purged and then it was treated with soap and it was purged, the pure articles with which it came into contact contract impurity. Although soap removes tints as well, since the garment was not treated with all seven detergent agents, it is presumed that it was a bloodstain and that, had the seventh agent been used, it would have been purged.
If one treated a stained garment with all seven detergent agents and the stain was not purged and then treated it with them again and it was purged, but a trace remained, all of the pure articles with which it came into contact between the first washing and the second washing are pure. All of the pure articles with which it came into contact after the second washing are impure. The rationale is that since he showed his intent that he objects to any trace of the stain and desires to remove all remnants of it, the garment is impure until all remnants are nullified and it is immersed in a mikveh.
In Hilchot Issurei Bi'ah, we already explained the seven detergent agents with which a stain is treated and how it is treated with them.

When a woman dies and afterwards menstrual blood flows from her body, it imparts impurity to garments it stains. The rationale is that the uterus is an impure place. Hence, even though the blood flowed out after she died and the laws of nidah no longer apply, since it emerged from an impure place, it imparts nidah impurity to garments it stains. If it comprises a revi'it, it imparts impurity to everything under the same shelter and it imparts impurity to garments it stains.