I know it's an awful thing to say on Mother's Day, and I certainly don't believe it myself. (Honest Mom!) But the God of the Bible does. There's a whole chapter about it in Leviticus. Here's what it says.
And the LORD spake unto Moses, saying, ... If a woman have conceived seed, and born a man child: then she shall be unclean seven days. ... And she shall then continue in the blood of her purifying three and thirty days. ... But if she bear a maid child, then she shall be unclean two weeks, as in her separation: and she shall continue in the blood of her purifying threescore and six days. Leviticus 12:1-5
So the proud, new mother of a baby boy is unclean for a week and must purify herself for 33 days after her son is born. And if the baby is a girl, the mother is twice as dirty; she is unclean for two weeks and must be purified for 66 days after giving birth. (The take-home message here is that, to God, girls are twice as dirty as boys.)
But a new mother is not only dirty to the biblical God; she is sinful, as well. So sinful, in fact, that she must sacrifice a lamb as a burnt offering and a dove as a sin offering (or two doves if she can't find a lamb to kill).
And when the days of her purifying are fulfilled, for a son, or for a daughter, she shall bring a lamb of the first year for a burnt offering, and a young pigeon, or dove, for a sin offering. ... And if she be not able to bring a lamb, then she shall bring two turtles, or two young pigeons; the one for the burnt offering, and the other for a sin offering. Leviticus 12:6-8
Happy Mother's Day (to all you dirty, sinful mothers out there)!