Sforno on Leviticus 15:19/ספורנו על ויקרא ט״ו:י״ט

1ואשה כי תהיה זבה דם, here the Torah teaches rules concerning the menstruating woman and the one afflicted with untimely discharges from her vagina, stating that purification of the latter requires two offerings, a sin offering and a burnt offering. The Torah testifies by the nature of the offerings required that the disease described “does not come out of the blue,” but was the result of improper thoughts or even improper actions which preceded it. Original woman who was punished for her sin was not only punished for eating from the tree of knowledge, but for the thoughts which ran through her mind prior to translating sinful thought into sinful action. We believe that this is reflected in the wording of the punishment הרבה ארבה עצבונך, “I will greatly multiply your discomfort” (during pregnancy and giving birth) (Genesis 3,16) The punishment fitted the crime which was not something that was the result of a sudden impulse. The seven days until purification from the date of the end of the state of zavah is achieved, gives her time to reflect and to think pure thoughts as opposed to the time she had originally spent before violating G’d’s commandment not to eat from that tree. When the proper thoughts course through her mind during these seven days called appropriately שבעה נקיים, seven days of purification, her mind and not only her body will have been cleansed from improper attitudes so that the ritual immersion cleanses both body and mind. When this is the case, the two offerings required by the zavah will bring her the atonement for previous misdemeanours both in thought and in action. The sin offering atones for sinful action, the burnt offering for forbidden thoughts.