Leviticus 15:19–24, The laws of niddah apply to a women in her menstrual cycle. This is an area that many take for granted, but not YHVH in his Torah. A woman’s body produces life or death depending on whether an egg has been fertilized or not during her monthly cycle. There are many spiritual ramifications to this, and YHVH does not treat this matter lightly. While her egg is passing from her body she is in a state of impurity since, in a sense, death is occurring (an unfertilized egg is passing out). It is a time of grieving and emotional turmoil for the woman. This is NOT the time for a man to approach his wife. To do so, as already noted, is strictly forbidden (Lev 18:19).
Consider the benefits to the marriage of the husband and wife separating themselves sexually and emotionally at this time each month, and how it can benefit and enrich a marriage. The man learns self control and selflessness in that he is given the opportunity to be extra solicitous of his wife’s needs without expecting anything in return. What’s more, how much sweeter their time of intimacy will be when the do come back together intimately. The old adage, absence makes the heart grow fonder, could apply here.
The Torah considers a woman to be unclean for at least seven days, even if her flow lasted only one day. So at the minimum a man is to be separated from his wife (giving her an emotional break) for at least seven days, if not longer. On the eighth day (at the minimum) or the next day after her flow has stopped, she is no longer considered unclean (The ArtScroll Tanach Series Vayikra, p. 247). Eight is the biblical number signifying new beginnings. In this case, eight relates to the new cycle of life that begins as the woman’s body begins to produce a new egg with the potential for new life to occur.