Leviticus 12-15. Ceremonial Purifications
The Purifications of the Law fall under three heads;
(1). Those for defilement arising from secretions;
(2). Those for the leprosy;
(3). Those for pollution from corpses.
The first and second classes are described in these chapters; the last, as relates to human corpses, in Numbers 19:11, etc., and as relates to the bodies of dead animals, in Leviticus 11:24-28, Leviticus 11:31-40.

Ordinances concerning the purification of women after child-birth, Leviticus 12:1; after the birth of a son, who is to be circumcised the eighth day, Leviticus 12:2, Leviticus 12:3. The mother to be considered unclean for forty days, Leviticus 12:4. After the birth of a daughter, fourscore days, Leviticus 12:5. When the days of her purifying were ended, she was to bring a lamb for a burnt-offering, and a young pigeon or a turtle-dove for a sin-offering, Leviticus 12:6, Leviticus 12:7. If poor, and not able to bring a lamb, she was to bring either two turtle-doves or two young pigeons, Leviticus 12:8.

INTRODUCTION TO LEVITICUS 12
This chapter treats of the purification of a new mother, the time of whose purification for a man child was forty days, and for a maid child eighty, Leviticus 12:1 at the close of which she was to bring her offerings to the priests, to make atonement for her, Leviticus 12:6.

Ceremonial purification.

Laws of Purification - Leviticus 12-15
The laws concerning defilement through eating unclean animals, or through contact with those that had died a natural death, are followed by rules relating to defilements proceeding from the human body, in consequence of which persons contaminated by them were excluded for a longer or shorter period from the fellowship of the sanctuary, and sometimes even from intercourse with their fellow-countrymen, and which had to be removed by washing, by significant lustrations, and by expiatory sacrifices. They comprised the uncleanness of a woman in consequence of child-bearing (Leviticus 12:1-8), leprosy (ch. 13 and 14), and both natural and diseased secretions from the sexual organs of either male or female (emissio seminis and gonorrhaea, also menses and flux: ch. 15); and to these there is added in Numbers 19:11-22, defilement proceeding from a human corpse. Involuntary emission defiled the man; voluntary emission, in sexual intercourse, both the man and the woman and any clothes upon which it might come, for an entire day, and this defilement was to be removed in the evening by bathing the body, and by washing the clothes, etc. (Leviticus 15:16-18). Secretions from the sexual organs, whether of a normal kind, such as the menses and those connected with child-birth, or the result of disease, rendered not only the persons affected with them unclean, but even their couches and seats, and any persons who might sit down upon them; and this uncleanness was even communicated to persons who touched those who were diseased, or to anything with which they had come in contact (Leviticus 15:3-12, Leviticus 15:19-27). In the case of the menses, the uncleanness lasted seven days (Leviticus 15:19, Leviticus 15:24); in that of child-birth, either seven or fourteen days, and then still further thirty-three or sixty-six, according to circumstances (Leviticus 12:2, Leviticus 12:4-5); and in that of a diseased flux, as long as the disease itself lasted, and seven days afterwards (Leviticus 15:13, Leviticus 15:28); but the uncleanness communicated to others only lasted till the evening. In all these cases the purification consisted in the bathing of the body and washing of the clothes and other objects. But if the uncleanness lasted more than seven days, on the day after the purification with water a sin-offering and a burnt-offering were to be offered, that the priest might pronounce the person clean, or receive him once more into the fellowship of the holy God (Leviticus 12:6, Leviticus 12:8; Leviticus 15:14-15, Leviticus 15:29-30). Leprosy made those who were affected with it so unclean, that they were excluded from all intercourse with the clean (Leviticus 13:45-46): and on their recovery they were to be cleansed by a solemn lustration, and received again with sacrifices into the congregation of the Lord (Leviticus 14:1-32). There are no express instructions as to the communicability of leprosy; but this is implied in the separation of the leper from the clean (Leviticus 13:45-46), as well as from the fact that a house affected by the leprosy rendered all who entered it, or slept in it, unclean (Leviticus 14:46-47). The defilement caused by a death was apparently greater still. Not only the corpse of a person who had died a natural death, as well as of one who had been killed by violence, but a dead body or grave defiled, for a period of seven days, both those who touched them, and (in the case of the corpse) the house in which the man had died, all the persons who were in it or might enter it, and all the open vessels that were there (Numbers 19:11, Numbers 19:14-16). Uncleanness of this kind could only be removed by sprinkling water prepared from running water and the ashes of a sin-offering (Numbers 19:12, Numbers 19:17.), and would even spread from the persons defiled to persons and things with which they came in contact, so as to render them unclean till the evening (Numbers 19:22); whereas the defilement caused by contact with a dead animal lasted only a day, and then, like every other kind of uncleanness that only lasted till the evening, could be removed by bathing the persons or washing the things (Leviticus 11:25.).
But whilst, according to this, generation and birth as well as death were affected with uncleanness; generation and death, the coming into being and the going out of being, were not defiling in themselves, or regarded as the two poles which bound, determine, and enclose the finite existence, so as to warrant us in tracing the principle which lay at the foundation of the laws of purification, as Bhr supposes, "to the antithesis between the infinite and the finite being, which falls into the sphere of the sinful when regarded ethically as the opposite to the absolutely holy." Finite existence was created by God, quite as much as the corporeality of man; and both came forth from His hand pure and good. Moreover it is not begetting, giving birth, and dying, that are said to defile; but the secretions connected with generation and child-bearing, and the corpses of those who had died. In the decomposition which follows death, the effect of sin, of which death is the wages, is made manifest in the body. Decomposition, as the embodiment of the unholy nature of sin, is uncleanness κατ ̓ ἐξοχξήν; and this the Israelite, who was called to sanctification in fellowship with God, was to avoid and abhor. Hence the human corpse produced the greatest amount of defilement; so great, in fact, that to remove it a sprinkling water was necessary, which had been strengthened by the ashes of a sin-offering into a kind of sacred alkali. Next to the corpse, there came on the one hand leprosy, that bodily image of death which produced all the symptoms of decomposition even in the living body, and on the other hand the offensive secretions from the organs of generation, which resemble the putrid secretions that are the signs in the corpse of the internal dissolution of the bodily organs and the commencement of decomposition. From the fact that the impurities, for which special rites of purification were enjoined, are restricted to these three forms of manifestation in the human body, it is very evident that the laws of purification laid down in the O.T. were not regulations for the promotion of cleanliness or of good morals and decency, that is to say, were not police regulations for the protection of the life of the body from contagious diseases and other things injurious to health; but that their simple object was "to impress upon the mind a deep horror of everything that is and is called death in the creature, and thereby to foster an utter abhorrence of everything that is or is called sin, and also, to the constant humiliation of fallen man, to remind him in all the leading processes of the natural life-generation, birth, eating, disease, death - how everything, even his own bodily nature, lies under the curse of sin (Genesis 3:14-19), that so the law might become a 'schoolmaster to bring unto Christ,' and awaken and sustain the longing for a Redeemer from the curse which had fallen upon his body also (see Galatians 3:24; Romans 7:24; Romans 8:19.; Philippians 3:21)." Leyrer.