When to Prepare for Mikveh Immersion
By Torah law, a woman must inspect her body and hair for barriers (chatzitzot) immediately before she immerses in the mikveh. Before this inspection (iyun), she must cleanse herself (chafifah). The Talmud cites two opinions regarding the timing of this cleansing (chafifah) – either at night, right before the inspection before the immersion, or earlier during the afternoon, so that she does not prepare hastily or carelessly under time pressure. The preferred way is to follow both opinions, by starting during the day and continuing into the night. But if circumstances (e.g., work, young children, lack of warm water) make this difficult, either alternative is acceptable.
Sometimes, the timing of chafifah is affected by other halachic considerations. Many elements of preparation (e.g., washing hair, cutting nails) are not permitted on Shabbat or Yom Tov. Therefore, a woman who will immerse on Friday night must complete all her preparations during the day. A woman who will go to the mikveh Saturday night should do a complete chafifah on Friday afternoon, be careful over Shabbat not to entangle her hair and then repeat a brief chafifah and final haircombing on Saturday night.
A woman who will immerse on the second night of Yom Tov, on Friday night following a Yom Tov, or on Yom Tov following Shabbat, must prepare on the last available weekday – even if this is several days before her immersion. Immediately prior to immersion, she should clean her teeth, separate strands of her hair with her fingers, and wash any parts of her body that may have become dirty, being careful to observe all the relevant Shabbat or Yom Tov restrictions.
In all circumstances, she must inspect herself immediately before she immerses.