אִשָּׁה֙ כִּ֣י תַזְרִ֔יעַ וְיָלְדָ֖ה זָכָ֑ר וְטָֽמְאָה֙ שִׁבְעַ֣ת יָמִ֔ים כִּימֵ֛י נִדַּ֥ת דְּוֺתָ֖הּ תִּטְמָֽא׃ וּבַיּ֖וֹם הַשְּׁמִינִ֑י יִמּ֖וֹל בְּשַׂ֥ר עׇרְלָתֽוֹ׃ וּשְׁלֹשִׁ֥ים יוֹם֙ וּשְׁלֹ֣שֶׁת יָמִ֔ים תֵּשֵׁ֖ב בִּדְמֵ֣י טׇהֳרָ֑הֿ בְּכׇל־קֹ֣דֶשׁ לֹֽא־תִגָּ֗ע וְאֶל־הַמִּקְדָּשׁ֙ לֹ֣א תָבֹ֔א עַד־מְלֹ֖את יְמֵ֥י טׇהֳרָֽהּ׃ וְאִם־נְקֵבָ֣ה תֵלֵ֔ד וְטָמְאָ֥ה שְׁבֻעַ֖יִם כְּנִדָּתָ֑הּ וְשִׁשִּׁ֥ים יוֹם֙ וְשֵׁ֣שֶׁת יָמִ֔ים תֵּשֵׁ֖ב עַל־דְּמֵ֥י טׇהֳרָֽהֿ׃ וּבִמְלֹ֣את ׀ יְמֵ֣י טׇהֳרָ֗הּ לְבֵן֮ א֣וֹ לְבַת֒ תָּבִ֞יא כֶּ֤בֶשׂ בֶּן־שְׁנָתוֹ֙ לְעֹלָ֔ה וּבֶן־יוֹנָ֥ה אוֹ־תֹ֖ר לְחַטָּ֑את אֶל־פֶּ֥תַח אֹֽהֶל־מוֹעֵ֖ד אֶל־הַכֹּהֵֽן׃
When a woman at childbirth bears a male, she shall be impure seven days; she shall be impure as at the time of her condition of menstrual separation.— On the eighth day the flesh of his foreskin shall be circumcised.— She shall remain in a state of blood purification for thirty-three days: she shall not touch any consecrated thing, nor enter the sanctuary until her period of purification is completed. If she bears a female, she shall be impure two weeks as during her menstruation, and she shall remain in a state of blood purification for sixty-six days. On the completion of her period of purification, for either son or daughter, she shall bring to the priest, at the entrance of the Tent of Meeting, a lamb in its first year for a burnt offering, and a pigeon or a turtledove for a purgation offering.
David Kraemer, The Logic of Impurity (Source)
[...T]he impure animals are “impure” because they belong, in their entirety, to God. In other words, marking something as “impure” means marking it as being somehow in God’s realm, touchable but in some profound sense inaccessible to us. We cannot eat the “impure” animal (the pig, for example) because God, its creator, has not given us the right to do so. Its impurity marks it as “out of bounds.”
By the same token, life and death are in the realm of God. As the Bible says repeatedly, in one form or another, “God gives life and God takes away life.” Both, therefore, are marked as “impure.” The same is true of menstrual blood, which emerges from “the source” of human life, deep in the womb, and the same is true of birth blood — the blood that issues forth when a woman gives birth. Not surprisingly against the background of this explanation, it is also true of semen, which likewise contributes to the making of life. In contrast, neither urine nor feces is impure because, while both might be “unclean” (an unfortunate translation of “tameh”), neither is in the realm of God. But “leprosy” is impure because it was understood to be an outbreak of death in life, and, as we have said, death is in the realm of God and is therefore impure.