The 75th mitzvah is that any zavah1 must bring an offering after she is healed from her discharge.
This offering, which consists of two doves or two young pigeons, is known as a korban zavah, and her atonement is incomplete2 until these sacrifices are brought.
Perhaps one will ask the following question: since the offering of the zav and that of the zavah are identical, we should count only the offering as the mitzvah, and everyone who is required to bring it would be included. [Therefore it would count just as one mitzvah rather than two.3] This is how we treated the sin-offering, the guilt-offering, the asham talui, and the offering of adjustable value4 — where we ignored the number of transgressions covered by each offering,5 and counted just the offering itself as one mitzvah. So too here, we should ignore the number of people who are required to bring this bird offering [and count only the offering itself]!
The explanation is that the offering of the zav and that of the zavah are not for transgressions, but are brought only because of specific physical conditions [and these differ by a man and by a woman]. If the physical condition of the man and that of the woman were identical — as their names, zav and zavah, are identical — then their sacrifices would be counted together [as one mitzvah]. However, this is not the case, for a man must bring an offering because he has emitted semen;6 but if something similar would be emitted by a woman, she would not become a zavah. [Conversely] in a woman, it is the flow of blood which makes her a zavah, and if a man would emit blood, he would be exempt from bringing a sacrifice. [The similarity is only their names, zav and zavah,] and the word zivus is associated with "flowing" — and not every flow is the same.
Our Sages7 said explicitly [that the flow of a zav differs from that of a zavah]: "A man becomes tameh through a white emission, and a woman becomes tameh through a red emission."
There is a clear proof that the law of a zav and zavah is unlike that of a leprous man and a leprous woman [whose offerings count as only one mitzvah8]. This is the statement of our Sages in tractate Kerisus,9 "There are four categories of "those whose atonement is incomplete": zav, zavah, a woman who has just given birth, and a leper." One sees clearly that the zav and zavah are counted separately, whereas the leper — whether male or female — is counted only once. This is because the zivus (flow) of a man is different from that of a woman [whereas the leprosy is the same].10
The verses11 which speak of her offering state, "When the woman is rid of her discharge...on the eighth day, she shall take for herself two doves."
