Q. When Orthodox Jews talk about “family purity”, what do they mean?
A. The Hebrew, taharat hamishpachah, covers the detailed laws of abstaining from sex during niddah – the monthly period of menstruation and the seven “clean” days – followed by immersion in the mikvah before the resumption of marital relations.
The laws of taharat hamishpachah are, like Shabbat and kashrut, commanded by the Torah.
Though not always easy to practise, taharat hamishpachah allows husband and wife to renew their marriage every month, it provides a time of privacy for the woman, and it challenges a couple to find non-physical ways of showing that they care for each other.
But the observance of these patterns is basically a Divine command which is followed out of love for the Creator and His Torah.