וידבר יי אל משה ואל אהרן. כי הכהנים יפרישו בין זבה לנדה כאשר אחז"ל בין דם לדם ועתה יחל לבאר הטמאים מדבר נסתר כי הצרעת נגע גלוי: AND THE LORD SPOKE UNTO MOSES AND TO AARON. For the kohanim distinguish between a woman who has an issue (zavah) and one who menstruates (niddah).1Hence this commandment was also communicated to Aaron. Compare the Rabbinic interpretation on between blood and blood2Deuteronomy 17:8-9 states that if there be a dispute regarding blood and blood then the kohen shall decide the aforementioned. The Rabbis interpret between blood and blood as meaning between “between menstrual blood and blood of an issue and blood of childbirth (Sifre, on Deut. 17:8).” (Deut. 17:8). Scripture now begins to deal with those who become unclean from a hidden source,3Such as an issue. for until now it dealt with leprosy which is a visible plague.