Midrash su Levitico 15:30

3) (Vayikra 5:7) "one for a sin-offering and one for a burnt-offering": (The dedication of) the sin-offering must precede (the dedication of) the burnt-offering. Alternately: that the burnt-offering be of the same species as the sin-offering (turtle-dove or young pigeon, respectively) (and that) if he separated his sin-offering and died, his heirs bring his burnt-offering. Alternately: What is the intent of "one for a sin-offering and one for a burnt-offering?" I might think that since two (birds) are brought in place of a (lamb) sin-offering, they should both be sin-offerings, it is, therefore, written "one for a sin-offering" — and not two; "one for a burnt-offering" — and not two.

5) See Chapter 5:13 (Vayikra 15:30) "And the Cohein shall make atonement for her before the L–rd from the flow of her uncleanliness": from the flow of her uncleanliness and not from the flow of her childbearing (See Tazria, Chapter 4:1).