Rational basis of religious rules
Some apparently strange religious rules can have a rational basis. The Jewish and Islamic ban on eating pork was probably very sensible in an age before meat inspection. More difficult to understand is the notion found in the Bible and the Koran that a menstruating woman is “impure”.
Leviticus states this unambiguously: “and anyone who touches her will be impure until nightfall (…) and everything on which she sits is impure (…) and anyone who touches her bed will be impure until nightfall (…) If a man lies with her (…) he will be impure for 7 days.”