Sifrei Mitzvot para sa Levitico 15:29

That is that He commanded us that any woman who is healed from a discharge offer a sacrifice and that is two turtledoves or two young pigeons. And this is the sacrifice of the zavah; and she is lacking [full] atonement until she offers it. And perhaps the questioner will challenge me and say, "Since the sacrifice of thezav is like the sacrifice of the zavah, why don't you [just] count the type of sacrifice that one is obligated, regardless of who is obligated, like you did with the sacrifice of the sin-offering, the definite guilt-offering, the variable guilt-offering and the variable sacrifice? As you counted each and every one as only commandment, each; and you did not concern yourself with the multiplicity of transgressions for which one is liable, such that one is liable a sacrifice for each and every one of them. So it would have been appropriate for you not to concern yourself with the multiplicity of [classes of] people that are liable for the fowl offering." And the verse that appears about this matter is His saying, "When she becomes clean of her discharge [...]. On the eighth day she shall take two turtledoves or two pigeons" (Leviticus 15:28-29). (See Parashat Metzora; Mishneh Torah, Offerings for Those with Incomplete Atonement 1-3.)

That a woman having an issue shall bring a sacrifice, after she is cleansed of her issue, as it is said, “But if she be cleansed of her issue….” (Lev. 15:28-30).

The commandment of the sacrifice of the zavah when she is healed from her discharge: That the zavah offer her sacrifice after she is healed from her discharge — and it is two doves or two young pigeons, as it is stated (Leviticus 16:28-29), “And if she is purified from her discharge, etc. And on the eighth day, she shall take two doves, etc.”