פירוש על קידושין 69:11

There are three derivations of the general rule—the first from a verse about atonement for accidental sins, the second about civil law, and the third about paying a ransom when an animal murders a human being. Why do we need all three?
The first would not be sufficient to teach that women are subject to all civil law because women did not engage in commerce as did men.
The second, about civil law, would not be sufficient to teach that if an animal kills a woman the owner must pay a ransom because women are not obligated in all commandments, as are men. (I know, this is a bit of an ugly one. But I do think it is a faithful representation of what happens when you exempt people from commandments. You might start to think that there life is less worthy than those fully commanded. This seems to be what might have happened to at least one strand of rabbinic thought).
If all we had was the third rule we might have thought that in that case, men and women were equated because it is a matter of life. But in cases of atonement or civil laws, they are not equal. Therefore we need all three derivations to teach that they are equal in all negative commandments.