The Shivah Neki'im (seven blood-free days)

A niddah who wishes to return to a state of taharah (ritual purity) must first perform a hefsek taharah to ascertain that all bleeding has ceased. She must then ascertain that bleeding has not recurred during the following seven days, before she may immerse in the mikveh. These days are known as the shivah neki'im, which is literally translated as "seven clean days." Since the status of niddah has nothing to do with physical cleanliness, "seven blood-free days" may be a better translation. A woman during this time period is said to be "counting the shivah neki'im," even though she is not obligated to actually enumerate each day.

While she is counting the seven blood-free days, a woman must wear clean white underpants and should sleep on white sheets. (It is customary, but not strictly required, to use white sheets even if she sleeps with tight-fitting white underwear.) For this reason, the seven blood-free days are sometimes called levanim, "her white days."

During the shivah neki'im, a woman must perform a series of internal examinations (bedikot), to verify that the bleeding has not recurred. She should do two bedikot each day, one upon arising in the morning (preferably after sunrise), and one in the afternoon, before sunset. If during the intermediate days she forgets one, or even both daily examinations, she may usually continue counting. Indeed, if the examinations cause her pain, or if she is particularly susceptible to spotting or has other difficulties, a rabbi may permit her to reduce their number depending on her particular circumstances. The examinations on the first and seventh days, however, are critical, and if she omits both examinations on either day, she may have to postpone her immersion (although she should consult with a rabbi or yoetzet first).

If even a trace of blood is found in one of the internal examinations, or if she discovers a stain which meets the conditions required for ketamim, then the entire count of seven blood-free days is invalidated and the woman must start over with a new hefsek taharah. If, however, she has even the slightest doubt about her status, she should not decide on her own that her count was invalidated, as her decision itself may have halachic ramifications. Rather, she should consult a rabbi about the problematic bedikah or stain, and continue with her count until she receives a definite answer, keeping in mind that a subsequent bedikah may if necessary be a new hefsek taharah, .

According to the view followed in most communities, the shivah neki'im may not begin until at least five days have passed since the woman became niddah. Therefore, a woman who has short menstrual periods, or who becomes niddah outside her period as a result of spotting, must be careful not to start her seven blood-free days until the sixth day from the onset of her niddah status. The custom in certain Sephardic communities, however, is to wait only four days, and even in other communities a rabbi may permit a woman to follow this view in extenuating circumstances, such as fertility problems.