Lévitique 12:2

Speak with the sons of Israel, saying: When a woman hath conceived and borne a male child, she shall be unclean seven days, as the days of the removal of her uncleanness shall she be unclean.

When a woman conceives After completing the laws of ritually pure and ritually impure food, Scripture now discusses ritual impurity among people, beginning with the law of the new mother, because birth is a beginning. Many people claim that when a woman releases her egg before the man releases his sperm, she will give birth to a boy; and they cite this verse, pointing out “When a woman conceives…and gives birth to a boy”. The sages of Greece are of this opinion — that the woman contains the seed, while the man’s sperm is a congealing agent, and that children are congealed from the blood of the woman.

conceives literally, “yields seed” because in her reproductive function she resembles the Earth [Genesis 1:11]. The vav of she will become impure is like the f of Arabic [comment on 11:45]. The reason for her seven days of ritual impurity is that we wait for her to enter the next lunar quarter (we also find, in the course of an illness, that changes are seen after every seven days).

separation a noun derived from an ‘ayin- ‘ayin verb, like “spoils” [Esther 9:15].

her indisposition similar in meaning to “sickness”, as in “the ailments of Egypt” [Deuteronomy 7:15], because the menstrual blood is an unhealthy part of the woman’s body

Rashi commented: “If a woman have conceived seed, and born [a male]. This includes a case where she gave birth to [the male child as] a fleshy mass which had dissolved, so that it became liquefied and like seed, in which case his mother becomes impure because of the birth” [as if it were a normal child]. The explanation of this matter is that we know that the child has been formed already in human form, and then became liquefied, for anything that does not have a human form is not considered a child, and similarly, whatever is not fit to become a creature with a soul, is not considered a child. But even if it is a fleshy dissolved mass at the time of birth, it makes the mother impure [for the prescribed number of days] provided we recognize its form, such as a foetus with its human parts fashioned, in which case the mother is certainly impure, and if not [i.e., the matter is in doubt] she is impure because of a doubt. This is what this verse comes to include according to the words of our Rabbis.
Now with regard to the implication of the verse the Rabbis have said:, 31a. “Ishah ki thazria — if the woman emits seed first, she will bear a son.” The intent of the Rabbis was not that the child is formed from the woman’s seed, for although the woman has generative organs [i.e., ovaries] like those of the man, yet seed is not formed by them at all, or [if it is formed], that seed is not thick and does not contribute anything to the embryo. Rather, the Rabbis used the term “she emits seed” with reference to the blood of the womb, which gathers in the mother at the time of the consummation of coition, and attaches itself to the seed of the male. For in the opinion of the Rabbis the child is formed from the blood of the female and the white [semen] of the man, and both of them are called “seed.” Thus the Rabbis have said:, 31a. “There are three partners in [the formation of] man: The male emits the white [semen], from which are formed the sinews, the bones, and the white substance in the eye. The female emits a red secretion from which are formed the skin, the flesh, the blood, the hair, and the black substance in the eye.” The opinion of doctors as to the formation [of the embryo of the child] is also the same. In the opinion of the Greek philosophers, however, the whole body of the child is formed from [the substance of] the blood of the mother, the father only contributing that generative force which is known in their language as hyly, which gives form to matter., p. 23. For there is no difference at all between the egg of a chicken which is laid because it was fructified by a male, and that laid as a result of the mother rolling herself in the dust, except that the egg [that had been fructified by a male] germinates into a young bird, while the other is not sown, nor beareth, because it is deprived of the elemental heat which is its hyly. And if so, the word tazria [in ishah ki thazria] will be like u’cheganah zeiru’eha thatzmiach (as the garden causeth the seeds that are sown in it to spring forth). can be understood in its simple meaning: “when the female emits her secretion” first etc. But according to the philosophers who say that the child is formed entirely from the body of the mother, and the male semen is merely a generative force which gives form to matter, then the word tazria can no longer mean “emitting,” but is like thatzmiach — “causes to spring up.” And so did Onkelos render it: “If a woman conceives.”

אשה כי תזריע, who becomes pregnant whether with a male fetus or a female fetus. When the time comes for her to give birth, the sex of the baby determines her status as to the impurity known as טומאת לידה. All the details are spelled out in the verses following.

שבעת ימים; even if it was a “dry birth,” no blood emerging from her vagina.

כימי נדת דותה, just as the red colour of the blood determines if a menstruating woman is still evacuating blood, so the same criteria apply to a woman giving birth. The whitish fluid that is characteristic a of woman in a state of flux, זובה, another source of ritual impurity originating within her body, is irrelevant to the subject under discussion in our verses.

נדה, the expression denotes a type of isolation, distance from her husband.

דותה, an expression denoting a kind of sickness. Compare Jeremiah 8,18 לבי דווי, “my heart is sick within me.”

אשה כי תזריע וילדה זכר, the sages in Niddah 31 explain the term תזריע in our verse as “when a woman experiences her orgasm before her male partner the child born from such a union will be a male. The perception underlying this is that the woman’s “seed” is the moisture which she excretes from time to time at the time she engages in physical union with her partner does not enter into the formation of a male embryo. Her “semen” is active in suppressing the effect of the man’s semen. But her blood enters the semen of the male it moistens and provides addition impetus to the man’s semen,

כימי נדבת דותה, for during the first seven days after her giving birth she is like a menstruating woman regarding her ritual status.

אשה כי תזריע, “when a woman conceives, etc.” what is meant here is that if the woman reaches orgasm in her marital relations with her husband before he does, she will give birth to a male child.