A woman must wait five days from the time she becomes niddah until she can begin counting the seven blood-free days. The custom in some Sephardic communities is to wait only four days.
A woman must wait five days from the time she becomes niddah until she can begin counting the seven blood-free days. She counts the day on which she became niddah as the first of these five days, and then counts four full days which last from sunset to sunset. Thus, a woman who becomes niddah on Sunday may do her hefsek taharah on Thursday – the fifth day – and begin counting her seven blood-free days on Friday – the sixth day. It does not matter whether she began to bleed on Saturday night, on Sunday afternoon, or at any other time between sunset on Saturday and sunset on Sunday. Therefore, a woman whose menses are short, or who has become niddah because of mid-cycle staining, must be careful not to start her seven blood-free days until the sixth day from the onset of her niddah status.
The source of this halacha is as follows:
Women commonly expel semen for a few days after intercourse. A day on which this occurs cannot be counted as one of the seven blood-free days. A woman who is unaware that she has expelled semen may mistakenly count the cancelled day and immerse in the mikveh too early. Because such an immersion would be invalid, she might unknowingly violate the laws of niddah.
From a halachic standpoint, semen is considered viable for 72 hours, after which it has no further halachic significance. Therefore, to be certain there can be no seminal expulsion during the seven blood-free days, at least 72 hours must elapse from the time a woman has intercourse until she begins to count. Moreover, since the 72 hours may begin in the middle of one calendar day and extend to the middle of the fourth day, she cannot start to count the seven blood-free days until the fifth day.
Accordingly, some Sephardic authorities permit women to begin the seven blood-free days on the fifth day (not the sixth, as above). The custom in most communities, however, is to wait an additional day, to avoid problems should a woman have intercourse shortly after sunset, and – thinking that she completed it before sunset – mistakenly count the outgoing day as the first of the four days.
Because the fifth day is an additional stringency, it does not apply to hymenal bleeding, after which a four-day wait is sufficient. Moreover, even for a regular niddah, a rabbi may allow a wait of only four days under extenuating circumstances – for example, if the couple has great difficulty conceiving.
The five-day minimum wait prior to the onset of the shivah neki'im applies even where the woman did not actually have intercourse for some time before becoming niddah. If, however, she was halachically forbidden to have relations (e.g., during the week of shivah, or on Yom Kippur) on the day or days immediately preceding the onset of her period, she may be permitted to count such days towards the five days, and a rabbi should be consulted.
Beginning the Five Day Minimum
One may begin counting the shivah neki'im no earlier than the sixth day from the onset of niddah. The practice in some Sephardi communities is to begin counting a day earlier, on the fifth day, see above.
The five day minimum was instituted to avoid any possibility of expulsion of semen during the shivah neki'im. Therefore, in some Sephardi communities, the minimum days are counted from the last time the couple had relations before niddah. In other Sephardi communities, and for all Ashkenazim, the minimum days begin with the onset of niddah - even if the couple did not have relations towards the end of her cycle. This decree ensures unity of practice and applies even if relations were completely impossible before the woman became niddah (e.g., the husband and wife were in different cities).
The five day minimum begins from the day a woman enters the status of niddah, even if the cause is not a flow. Therefore, if she becomes niddah from a stain on clothing or a bedikah cloth, or from a medical procedure, the day she becomes niddah is day one of the five day minimum.
In fact, the five day minimum begins from the point one acts as if one is niddah. Thus, for example, a woman discovers a questionable stain on Monday and tells her husband that she might be niddah. On Tuesday, before she has received a ruling on the stain, she begins her menses and is definitely niddah. She may count Monday, the day she acted as niddah, towards the five day minimum - even if the stain in retrospect would have been permissible.
Questions arise when relations are halachically forbidden for reasons other than niddah - can those days be counted towards the minimum? There is some halachic debate in this area, so in practice an individual question should be asked to one's own rabbi. We will explore several such situations one by one.
Marital relations are forbidden when either the wife or husband is sitting shivah. If the wife becomes niddah during aveilut, some halachic authorities would allow the five days to begin from the onset of aveilut, while others would not.
Yom Kippur or Tisha B'Av
Marital relations are forbidden on Tisha B'Av and Yom Kippur. If a woman becomes niddah during a nighttime onat perishah immediately following one of these fast days - so that relations were prohibited continuously for the 24 hour fast day and the following night - some poskim allow the fast day to be considered the first day of the five day minimum.
Marital relations are forbidden on veset days (onot perishah). If a woman has a full 24-hour veset immediately followed by another veset, and becomes niddah during the second veset, she may be able to count her five days from the beginning of the first veset. This situation can apply to those who keep onah beinonit for 24 hours and have another onat perishah come out the following evening. It can also apply to women who keep the onah of the Or Zarua prior to every veset, have two of these come out back to back, and start to bleed during the latter one.
Similarly, women who consistently have staining prior to the onset of actual bleeding may be able to consider this a veset haguf. Here as well, if the actual flow began during her veset haguf, the days of separation due to the veset may be counted towards the five day minimum.
When a couple abstains from relations "just to be on the safe side" for or for an individual minhag (as opposed to one established in the community), then this day does not count toward the five day minimum. In some cases, the distinction between halachic prohibition and careful practice is not obvious. In those cases, an individual halachic question should be asked. It should be also noted that in extenuating circumstances, such as difficulty conceiving, the rulings may be different and an individual halachic question should be asked.
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