Musar su Levitico 12:5

It is well known that the real reason Cain killed Abel was on account of a female, Abel's additional twin-sister. It is understandable then that the Torah legislates that a woman who gives birth to a female child has to remain ritually impure for fourteen days instead of the seven days she remains impure when she gives birth to a male child (Leviticus 12,5). The reason that she is granted a period of thirty-three days if she gave birth to a boy or sixty six days respectively if she gave birth to a girl during which any blood seen by her is not considered as causing impurity, (although she is not yet totally pure again), is hinted at in connection with the birth of Cain and Abel in sacred texts of the Kabbalists.