Niddah Womens Cycles
The full instruction on Niddah appears only once in Torah. In the book of Leviticus, the 19th through 33rd verses of the 15th chapter discuss a womans menstruation, uncleanness, and the instructions for niddah, which means separation. While unclean can be symbolic of sin, menstruation has nothing to do with sin. There is nothing wrong with menstruation. [Menstruation has been incorrectly translated as sickness in some places in the scriptures.]
The word niddah [Strongs 5079] has also been translated as flowers in the King James Version of the Bible. In that context, it means menstrual blood.
Leviticus 18:19, 20:18, and 15:24 instruct the man not to have intercourse with his wife during her unclean time. The passage in Leviticus 15:28 is generally translated to mean, once a womans menstrual discharge has stopped, she should be considered unclean for an additional seven days. However, others translate it as being unclean for seven days from the time the menstrual discharge commences.
The people of Elohim were not to follow the practices of the Egyptians, Canaanites, or others. Among their practices was the ritual of drinking menstrual blood.
Physical reasons
In order to understand the physical reasons behind niddah, we must understand the nature of menstruation, as well as the menstrual cycle. There are physical reasons for not touching or being touched intimately during menstruation.
Menstrual fluid is a combination of discarded cells of the endometrium, mucous, blood, and bacteria. Menstrual blood also contains whatever viruses may be in a womans bloodstream [such as HIV, Hepatitis, or other communicable viruses]. If menstrual blood backs up into the Fallopian tubes it causes infection, known as pelvic inflammatory disease. One of the physical reasons for avoiding contact with menstrual discharge is because it is potentially infectious.
Another physical reason for abstaining from intercourse during menstruation has to do with the changes that occur in the vagina during that time. The vaginal lining partially sloughs off, also, and is reduced to the very thin basal layer. This thin layer is fragile, and very vulnerable to micro-trauma and tearing from friction [such as is produced during intercourse]. During other times in the month, the vaginal lining is three layers thick, and relative unsusceptible to injury.
Spiritual reasons
In the spiritual sense, niddah is symbolic of impurity. The word unclean means ritual impurity. It is emblematic of that which is wasteful, unfulfilled, unprepared, etc. In order to understand the spiritual reasons for niddah, we need to recognize some symbolic or spiritual things about the womb, and the cycle from menstruation to ovulation.
The womb is a vessel, and can be compared to the mind, the heart, or ones life, in general. The womb is literally a container. At times during the menstrual cycle, the uterus is fertile and receptive to seed, and able to foster growth and new life. During menstruation, however, the uterus is unprepared to receive and sustain life. The menstrual cycle is a type and shadow of the cycles we go through during our lives.
The uterus, as a metaphor of our mind or heart, is either prepared or unprepared to receive the seed of Elohim. The seed may be compared with the spirit, the beginning of the knowledge of the plan of redemption, etc. The menstrual uterus is like an unprepared or unreceptive heart or mind.
The Moon and the Menstrual Cycle
There is a very close relationship between the moon and menstruation. In our present culture, women commonly refer to menstruation as having their monthly. Some more poetically refer to it as their moon time. Our word month comes from the same root-word as moon. The word menstruation comes from the Greek word menus, which means moon and power, and based upon men, which means month. The Hebrew word for month is the same as new moon. The womb in its phases is also linked to the moon in her phases. [The Hebrew words for moon, yareach and levanah, are feminine.]
Ovulation is likened to the full moon.
The monthly onset of menstruation may be likened to the new moon a time of introspection, preparation [the empty & purged vessel]. It is a time of starting again, renewal, and a time that may be set apart to devote extra time to spiritual pursuits.
The period of niddah was to be followed by mikvah ritual purification [much like baptism]. When the woman bathed at the conclusion of her menses, she became ritually pure. Traditional Jewish communities built a mikvah area even before they would build a synagogue.