Although the mikveh may appear to be merely a larger version of a bathtub, it is categorically not intended for purposes of cleanliness or hygiene.  Modern mikvehs are the work of experts in the laws of the mikveh working together with interior designers. They are constructed to be a delight to the eye, convenient to use, and easy to keep scrupulously clean. The designer takes into account a woman's need for privacy and utmost discretion. The mikveh is equipment for spiritual “hygiene”, not physical cleanliness. In preparation for immersion in the mikveh, the person is required to cleanse his body scrupulously, as detailed in the laws which follow. The Torah law provides full instructions as to how this should be done. 

The Torah tells us: “...only a spring or a cistern, a gathering of water, shall remain pure...” (Leviticus 11:36)

From this verse we learn the laws of how to construct a mikveh which is capable of cleansing anyone immersing in its waters from their spiritual impurity. The outstanding quality of the water in a mikveh, the sine qua non, which qualifies it to serve as a means of spiritual purification, is that the water be connected to its natural source, whether it is rainwater or a natural spring. The same water, if transported to the mikveh in buckets, for instance, has lost its power to effect a spiritual cleansing.

We remain with the basic question: How does immersion in something so simple as water wield so profound an influence on a person and the spiritual level on which he acts? Jewish literature provides a vast number of explanations. We will bring the reader a small selection of the shorter ones.

1.    Through association: We naturally think of water as a basic factor in cleansing our bodies, our homes, cars, offices - what have you. In short, water is equated in our minds with cleanliness. When a person immerses in the mikveh, physically, he has just finished cleaning his body. The mikveh represents the same process, but on a spiritual level. It whispers to the heart: “Cleanse yourself of all sin!” Contact with water stirs the heart and arouses one to strive for a higher moral standard of living (Sefer Hachinuch, Mitzvah 175).

2.    The bubble effect: When we take a bottle and immerse it entirely in a mikveh, the air inside the bottle will escape and rise to the surface. The water of the mikveh replaces it. So, too, when a person immerses himself completely in the mikveh, the spiritual contamination which surrounds a person escapes, rises to the surface, and disappears into thin air. One of the laws of mikveh stipulates that the person must be completely underwater when he immerses. Not a single hair of his head may be on or above the surface of the water. Rabbi Abraham Azulai, a renowned scholar of Kabbalah, gives us the following explanation: “...since man is a compound of four basic elements, the only way to cleanse him spiritually is through water, since spiritual contamination is a function of the spirit, which by its very nature, does not penetrate into water. (Air always rises above water.) When the person who is spiritually unclean enters the water, the spirit of contamination automatically detaches itself from him and dissipates.”

3.    Living waters: The presence of water is a prerequisite for life. When astronomers examine the atmosphere of a planet, one of their first questions will inevitably be: “Is there any evidence of the presence of water?” Only if some trace of water is found, will the scientist suspect that there may be some form of life on the planet.

The human body is built largely of water. An embryo is 97% water; in an elderly person, the percentage is reduced to 60%, as though to say, the more watery the body, the longer the life expectancy of the person. When a person is born, he leaves a sack of water in which he had floated and begins life on this earth. Just as an encounter with death brings spiritual contamination upon one, so, too, does an encounter with the waters of the mikveh bring purification and spiritual cleansing.

In order to qualify for use as a mikveh, the water must flow directly from its source into the mikveh. If it is collected in a pail or a barrel, for instance, and then carried to the mikveh and poured into it, the mikveh is no longer effective. Chemically, there is no change in the water; it is still H2O, but it has lost its quality of being able to dissipate spiritual contamination. Similarly, we find in the world of medicine, that water from mineral springs is more effective as a healer than is the same water when bottled and transported elsewhere. Similarly, Jewish law stipulates that the water for the mikveh not be poured into any container which is not connected to the source from which the water originally flowed. Water drawn from a well or a spring and then poured into the mikveh does not meet the requirements of Jewish law.

4.    The Womb of the Universe: In the realm of Kabbalah, we find that the mikveh symbolizes the womb. When one immerses in a mikveh, he is considered to have returned to the womb. He emerges from the water spiritually reborn and renewed. The world was created and formed from water, as we find in the first verse of Genesis: “In the beginning of G-d's creating the heavens and the earth, when the earth was confusing and empty, and darkness lay on the surface of the depths, and the spirit of G-d hovered over the water...” (Genesis 1:1-2)

This verse reveals that the universe was formed from the primeval waters of the genesis of the creation. Thus, the waters were the womb of the universe, waters over which the spirit of G-d hovered. In fact, all spiritual blessings which descend from Above and take form as physical entities are transmitted through water: the world, rainfall, and other forms of precipitation, and the embryo of living creatures. 

The verses which follow describe the act of Creation on the third day: “And G-d said: Let the waters beneath the heaven be gathered to one place, and the dry land will be seen. And it was so. G-d called the dry land, 'earth' and the gathering of the water, He called 'seas'” (Genesis 1;9-10).

The womb of the universe, as it were, was gathered to one spot. Henceforth, it was to be called the ocean. From here we learn that the word mikveh, which appears in this verse, refers to water in its original, primeval form. Natural waters are required for a mikveh, whether rain water, spring water, or water from the ocean.

At first, the water of Creation covered the entire face of the earth. It was only later, on the third day, that the waters receded and were gathered and assigned their place, at G-d's command. Nonetheless, they retain the power to again cover the face of the earth. What contains them? “The voice of G-d, over the waters” as we find in the Book of Psalms.

Anyone who strolls along a stretch of seashore senses the enormous force of the waters of the seas. An invisible borderline divides water from land. The waves race in, reach the border, break, and recede. This is a non-negotiable border, established by the Creator Himself. When the unspoken borderline is reached, the water recedes, and waves are formed when the incoming waters collide with those which are in retreat. That border is the Voice of G-d which continues to declare “Let the waters be gathered to one place...”

King David describes this wonder in his psalm, when says in praise of G-d's might: “You set a boundary they cannot overstep, they cannot return to cover the earth...” (Psalms 104:9)

Let us return to our explanation of the mikveh. When a person is entirely under the surface of the water, and “the Voice of G-d is upon the waters” (Psalm 29,) there is no longer any significance to man's outer appearance. At that moment he has returned to his most basic essence, as the verse in the beginning of Genesis tells us, “confusing emptiness.”  In this state, he is ready to be recreated and renewed by the Source of Life. When he leaves the mikveh, it is with a renewed point of birth. This is the source of his cleansing from contamination.

Indeed, as we find in the Sefer Hachinuch the reasons behind the commandments, we are commanded to immerse in the mikveh “...so that a person will view himself, after his immersion, as though he had just been born, as though the world were all water, before man came into being, as it says: And the spirit of G-d hovered over the surface of the water” (Mitzvah 173).

In the mikveh, man returns to the womb, to that point at which he left the world which was solely spiritual, and entered the physical world in which we now find ourselves. It is this quality of the mikveh which makes it possible for man to receive a new spiritual blessing as does a new-born babe. Everyone agrees that there is no one more innocent and pure than an infant. The moment of leaving the mikveh is the height of clinging to G-d. It is a moment of grace most suited to prayers which arise from the depth of the heart.

The quality of the bond between husband and wife depends on this moment. Therefore, it is the appropriate time to pray that the Creator will be with us and sanctify our bonding with our spouse; that He cause His presence to dwell in our home, and unite our souls in a union of true, everlasting love, a love that knows no barriers. All that separated us, the anger and the quarrels, has been swept away, left behind. When we rise out the waters of the mikveh, we are as a newborn, complete and perfect. We are full of joy, ready to enter the Holy of Holies of our personal Sanctuary, which is our home.

It is interesting to note that the idea of return to the womb in order to effect a change for the better has been adopted by modern psychology with considerable success.

The minimal amount of water which a mikveh must contain is forty se'ah (Talmudic measurement). We find references to the number forty mentioned in the Torah several times, alluding to spiritual renewal. For instance, the rains fell for forty days during the Flood of Noah, and changed the face of the earth completely. Moses our Teacher remained on the Mount of Sinai forty days and forty nights in order to receive the Torah. As a result, the Jewish nation was born. The Children of Israel wandered in the wilderness for forty years, until a new generation arose and entered the Land of Israel. From the first day of Elul, the final month of the year, until Yom Kippur, the Day of Atonement, we have forty days in which to repent, mend our ways, and turn over a new leaf. The halachah states that an embryo is called a fetus from the fortieth day after its conception.