“A woman with whom a man has carnal relations, they shall bathe in water and remain unclean until evening”
Leviticus 15:18

The functions of the mikveh, ritual bath, include conversion and preparation for Shabbat and festivals, but the mikveh is primarily associated with the purification of women following their menstrual period. In this regard, our parshah contains two surprises.

First, all but one of its many references to ritual bathing concern men, not women. Men must purify themselves in water after their own discharge, including semen; after having come into contact with the discharge of other men (via furniture, clothing, or spit); and after contact with menstrual discharge (via bedding or clothing). Second, Leviticus nowhere states explicitly that women should purify themselves following their own discharge, including menstrual. This could be, as Jacob Milgrom argues, because it is assumed that the rules applying to male discharge also applied to female discharge, but, in the absence of an explicit statement, that must remain a matter of speculation.

So what biblical evidence do we have that women bathed after menstruation? A popular prooftext is the account of David’s encounter with Bathsheba. II Samuel 11:2 reports that David saw Bathsheba bathing on the roof, and verse 4 mentions that David lay her, that she purified herself from her uncleanness (mi’tumatah), and that she went home. Surely, commentators reason, the reference to purification in verse 4 is a flashback to the roof bath — Bathsheba had just purified herself from menstrual uncleanness before lying with David?

But our parashah contains a much better explanation. The single law in Metsora that states explictly that a woman must purify herself in water does not concern menstruation, but rather carnal relations that involve emission of seed (shikhvat zera): “A woman with whom a man has carnal relations, they shall bathe in water and remain unclean (ve’tomu, cf mi’tumatah) until evening” (Leviticus 15:18).

In this light, 2 Samuel 11:4 is not a flashback to the roof bath, and does not concern menstruation, but rather describes what Bathsheba did following carnal relations with David, and prepares for the news of her pregnancy (there was emission of seed). Halachically speaking, mikveh and menstruation are inseparable. Biblically speaking, the search for an explicit, unambiguous reference to the post-menstrual mikveh must go on. Dr Diana Lipton