Water is the transformer and the giver of life, and for millennia people have used water to purify their bodies and possessions — literally, figuratively, and spiritually. Judaism has a long tradition of caring about ritual and spiritual purity, called taharah, stemming from the Biblical instructions regarding priests and sacrifices.
Because everyday observance of mitzvot and worship now replace the ancient sacrifices, you need to be ritually pure to participate properly. For example, Jewish law states that being in a room with (or touching) a dead person or animal makes you ritually impure.
When people become impure (tamay) for one reason or another, they can use a water ritual to become pure (tahor) once again. So, Jews often pour water from a pitcher over their hands before coming into the house of mourning after attending a burial.
Similarly, traditional Judaism states that while women are menstruating, and for seven days after they finish bleeding, they are tamay (so men and women don’t touch each other during this time). When this period is finished, the women immerse themselves in a mikvah, a ritual bath composed at least in part of fresh water (tap water doesn’t count as fresh).
Most Jewish communities have a “public” mikvah that people can go to, but any natural spring, river, lake, or ocean will do, too.
The mikvah (or the hand-washing ceremony prior to eating) isn’t meant to cleanse physically; participants must be physically clean beforehand. The mikvah is meant to provide a spiritual cleansing. Many observant Jews, both men and women, visit a mikvah each week, before Shabbat. Jews traditionally visit the mikvah just before getting married, too.
Many less-traditional women and men view the mikvah with suspicion because this ritual cleansing can be interpreted as “women are dirty and untouchable” after menstruation. It is believed that taharah has more to do with the affirmation of life, and the mikvah is a process of being born again and re-focusing on creation.
Not surprisingly, the mikvah is called for just before the woman is ovulating, and couples are reunited when the chance of pregnancy is highest. Use of the mikveh by Reform and Reconstructionist Jews is on the rise, particularly before conversions, wedding ceremonies, and even some holidays. Some liberal Jewish communities have also explored use of the mikveh for psychological healing.