Water as the source of life
Bereishit - Genesis - Chapter 1:6-7- And G-d said, "Let there be an expanse in the midst of the water, and let it be a separation between water and water. And G-d made the expanse and it separated between the water that was below the expanse and the water that was above the expanse, and it was so.
Mikvah as a chok
Bamidbar Rabbah 19:8- The dead body does not defile, and the water does not cleanse. Rather, G-d said, “I have issued an order, and made a decree – and no person may violate My decree,” as the verse states [Bamidbar/Numbers 19:2] (in reference to a law of ritual impurity), “This is the decree of the Torah...”
Mikvah- as a medium for cleansing
Vayikra - Leviticus - Chapter 14:8- He shall immerse himself in water and become pure…
The requirement for the “size” of a mikvah
Vayikra - Leviticus - Chapter 15:16- A man from whom there is a discharge of semen, shall immerse all his flesh in water, and he shall remain unclean until evening.
Immersion in Mikvah- 3 bodies of water
Vayikra - Leviticus - Chapter 11:36- But a spring or a cistern, a gathering of water remains clean. However, one who touches their carcass shall become unclean.
Niddah status after Birth
Vayikra - Leviticus - Chapter 12: 1-2- And the Lord spoke to Moshe, saying: Speak to the children of Israel, saying: If a woman conceives and gives birth to a male, she shall be unclean for seven days…”
Vayikra - Leviticus - Chapter 12: 5- And if she gives birth to a female, she shall be unclean for two weeks…”
Changing one’s status
Rabbi Aryeh Kaplan, Waters of Eden- One of the most obvious qualities of water is the fact that it is a liquid. Indeed, in a sense, water is the primary representation of the fluid state. In many instances, when we speak of “water” we are actually speaking of the fluid state in general. Therefore, the spiritual counterpart of water is very closely related to its property of being a fluid. But what is the main difference between a fluid and a solid? What special property does a fluid have that does not exist in the solid state? The main difference between them involves change. If only solids were to exist, there would be no change at all. The world would be a dead, airless body in an unchanging frozen state. For change to be possible, the fluid, as well as the solid state must exist… [W]e see that water itself represents the change and flow toward G-d’s goal. When a person immerses himself in a mikvah, he immerses himself spiritually in the basic concept of change itself. Man’s ego represents the element of his permanence, and therefore, when he is totally immersed in the concept of change, his ego is nullified. Thus, when he emerges from the mikvah, he is in a total state of renewal and rebirth.