Komentarz do Kapłańska 15:19

כי תהיה זבה AND IF A WOMAN HAVE AN ISSUE — One might think that this means: if there be an, issue from any limb of her body (e. g. ear, nose)! It, however, states in a law referring to this matter, (Leviticus 20:18) “and she hath uncovered the fountain of her blood” — only that issue of blood therefore makes her unclean which comes from her fountain (Sifra, Metzora Parashat Zavim, Section 4 2).

ואשה כי תהיה זבה דם, here the Torah teaches rules concerning the menstruating woman and the one afflicted with untimely discharges from her vagina, stating that purification of the latter requires two offerings, a sin offering and a burnt offering. The Torah testifies by the nature of the offerings required that the disease described “does not come out of the blue,” but was the result of improper thoughts or even improper actions which preceded it.
Original woman who was punished for her sin was not only punished for eating from the tree of knowledge, but for the thoughts which ran through her mind prior to translating sinful thought into sinful action. We believe that this is reflected in the wording of the punishment הרבה ארבה עצבונך, “I will greatly multiply your discomfort” (during pregnancy and giving birth) (Genesis 3,16) The punishment fitted the crime which was not something that was the result of a sudden impulse. The seven days until purification from the date of the end of the state of zavah is achieved, gives her time to reflect and to think pure thoughts as opposed to the time she had originally spent before violating G’d’s commandment not to eat from that tree. When the proper thoughts course through her mind during these seven days called appropriately שבעה נקיים, seven days of purification, her mind and not only her body will have been cleansed from improper attitudes so that the ritual immersion cleanses both body and mind. When this is the case, the two offerings required by the zavah will bring her the atonement for previous misdemeanours both in thought and in action. The sin offering atones for sinful action, the burnt offering for forbidden thoughts.

דם יהיה זובה, the reddish colour causes the ritual impurity here, not the whitish colour, suggesting seminal fluid.

Only saw one sighting. [This is] because “she shall be” is extra. This is what it means: “When a woman sees blood even one time, for seven days she will be in [the state of] her menstrual impurity.”

שבעת ימים תהיה בנדתה, “she will remain in her state of ritual impurity for a full seven days;” if she immerses herself before evening the immersion is not valid. (Talmud Pessachim, folio 90)

דם יהיה זובה בבשרה AND HER ISSUE IN HER FLESH BE BLOOD — Her issue does not come under the term “flux” to cause uncleanness except if it is red (cf. Niddah 19a).

בנדתה [SHE SHALL BE] PUT APART [SEVEN DAYS] — The word has the same meaning as, (Job. 18:18) “and they shall drive him out (ינדהו) of the world” — and her state is so called because she is set apart from the touch of any person (separated, so that no-one shall touch her).

תהיה בנדתה [SEVEN DAYS] SHALL SHE BE IN HER SEPARATION. even though she has seen a show of blood only once (lit., only the first show — i. e., not 7 days continuously) (Sifra, Metzora Parashat Zavim, Section 4 5).

That is that He commanded us that a menstruant woman be impure. And this commandment includes the impurity of the menstruant woman and all of her regulations. (See Parashat Metzora; Mishneh Torah, Those Who Defile Bed or Seat 4.)