Midrash su Levitico 12:7

1) I might think that also for birth and for zivah (uncleanliness) she brings one offering; it is, therefore, (to negate this) written "This (is the law for the woman who bears") (to exclude zivah from that offering). "whether a male or a female": to include a miscarriage of a sandal (a flat abortion), or a placenta, or an articulated sac. (Vayikra 12:8): "And if she has not means enough for a lamb": We do not tell her to borrow and not to ply her trade. If she has enough for a lamb but not for (its accompanying) needs, whence is it derived that she brings a pauper's offering? From "enough for a lamb," (connoting all that is necessary for a lamb).

2) This tells me (as not imparting tumah by carrying) only of the lesser forms of tumah (such as that of a sheretz (a creeping thing) or of carrion, which do not make a man tamei). Whence do I derive the same for graver forms of tumah, such as dead-body tumah, and that of cohabiting with a niddah, and all (forms of tumah) which make a man tamei? From "anything that is tamei" (imparts tumah to consecrated flesh) — even one who is lacking atonement (viz. Vayikra 12:7). R. Yossi said: Whence is it derived that fourth-degree tumah invalidates consecrated offerings, and that it follows a fortiori? (From the following:) If one lacking atonement, who is permitted to eat terumah, invalidates consecrated offerings, then third-degree tumah, which does invalidate terumah, does it not follow that it should invalidate offerings (in rendering it fourth-degree tumah)? We derive, then, (the invalidation of) third-degree tumah from the verse ("and the flesh that shall touch, etc."), and of fourth-degree tumah from the argument a fortiori.

2) "then she shall take two turtle-doves or two young pigeons": She brings two and not three (i.e., and not an additional one for the lamb that she brings if she is rich). (Why is a verse necessary for this?) Does it not follow? viz.: She brings from what she can afford, and a leper brings from what he can afford. Just as a (rich) leper brings one for one (a he-lamb for a burnt-offering and a ewe-lamb for a sin-offering, and, if he cannot afford that, two turtle-doves; one for a sin-offering, the other for a burnt-offering), she, too, brings one for one. — But, perhaps go in this direction: She brings from what she can afford, and tamei mikdash (one who eats consecrated food or enters the sanctuary) brings from what he can afford. Just as tamei mikdash brings two for one, (a rich man, a ewe-lamb for a sin-offering, and a poor man two turtle doves, one for a sin-offering and one for a burnt-offering, she, too, brings two for one. Let us see to what she is most similar. We derive one lacking atonement (a woman after childbirth) from one lacking atonement (a leper), and this is not to be refuted by tamei mikdash, who is not lacking atonement (i.e., even though he must bring an offering, he may still eat consecrated food before then) — But, perhaps go in this direction: We derive one (a woman after childbirth) whose "poor man" does not bring a beast (for a guilt-offering) from one (tamei mikdash) whose "poor man" does not bring a beast, and this is not to be refuted by a leper, whose "poor man" does bring a beast. It is, therefore, written "then she shall take two turtle-doves or two young pigeons." She brings two and not three.