I understand that the prohibition of approaching a woman who is nidah is from the Torah. However the wait of seven clean days is not , could u tell me the exact source for this prohibition ? Is it part of the precept to add boundaries to the Torah? ( By torah , i mean the 5 books of Moshe) Also if the this Halacha is coming from extrapollation , advise the original source. Thank you. Gabriel Ovadia

Shalom U'vracha The Torah speaks about two different types of discharge from the uterus. One is regular menstruation and the other is called ziva. According to the Torah a woman who menstruates has to count seven days and can then go to the mikvah. However a ziva who has seen this discharge for three days can only immerse in the mikvah after she has counted seven clean days. Today we do not know the difference between nidah and ziva therefore as this is a Torah prohibition we have to assume that each woman who sees any type of uteral bleeding is classed as a ziva and has to count seven clean days after the end of the bleeding. The Gemara brings this down as a set halacha that all accept therefore a woman today who bleeds must count seven clean days before she can go to the mikvah. Kol Tuv