All food that is eaten, upon which water comes, can be contaminated
In the 11th chapter of Leviticus the Torah discusses some of the laws of ritual impurity (tum'ah): food that comes in contact with a source of impurity (such as a corpse, a rodent, an object of idolatry, etc.) is thereby rendered ritually impure and disqualified from use in the Holy Temple and its service.
The above-quoted verse touches on two of the necessary conditions before a foodstuff is susceptible to contamination: 1) The food in question must be fit for human consumption. 2) It must first come in contact with water (or one of the other "seven liquids"); for example, grain that has been kept dry from the time it was harvested is not subject to tum'ah.
As man is a synthesis of body and soul, the Torah that instructs and inspires his life likewise possesses both a "physical" element as well as a conceptual-spiritual side. The "body" of Torah is its legal code and pragmatic guide to daily living; its "soul" is the inner dimension of these laws, which addresses the internal world of the human mind and heart, man's relationship with his Creator and his purpose in life.
The is also true of the laws regarding the ritual impurity of food. These, too, have a moral-spiritual application to our lives.
The first law recounted above--that only food that is fit for human consumption is open to contamination--expresses the idea that the loftier a thing, all the more vulnerable is it to corruption. Animal fodder is of a limited potential; equally limited are its negative uses. But the food that drives the human mind and heart can be the instrument of tremendous achievement; conversely, it may fuel the most destructive endeavors.
The same applies to all areas of life. A person may choose to "play it safe" and avoid anything touched by controversy, risk, or the possibility of failure---anything that may challenge his spiritual purity. But in doing so, he also disavows his most lofty potentials, the vulnerable but invaluable "human food" resources of his life.
Three Characteristics of Water
The second law specifies that food becomes susceptible to contamination only after having come in contact with a liquid. In other words, simply being fit for human consumption is not enough; unless the foodstuff has been wetted, it does not attain the high degree of potential that is indicated by the possibility of impurity.
In the spiritual sense this means that a "dry" life will always remain safely limited in scope and extent. In order to be in a position to truly realize its potential it must assume a "liquid" quality.
What are the specialties of the liquid state?
Three things characterize liquids: a) a liquid is an adhesive; b) a liquid is a conveyer; c) a liquid always seeks the lowest point of a terrain.
With the addition of liquid, powder becomes a paste, clay a pot, flour a loaf. Liquid is thus a unifier, bonding the dry particulars to a cohesive whole.
While food provides nourishment for our bodies, it would be utterly useless without the fluids that carry it to the body's every limb and cell (in the words of the Talmud, "He who eats without drink, his food is poison"). In other words, when transportation and integration is needed, be it in the human body or in a river valley, water is the medium of conveyance.
Finally, the solid is a snob. It clings to its station, descending to levels lower than itself only when forcefully dragged down. The liquid, however, naturally flows downward, seeping through the slightest of openings to transport itself from the highest elevations to the lowest plains.
A Fluid Life
The "dry" individual is egocentric, stagnant and jealous of his position. His life is series of "localized" deeds---deeds and achievements which have no effect beyond their immediate time and place, and which leave no lasting imprint on their performer. He stands alone, shunning connection and adhesion with his fellows, particularly with those inferior to himself.
On the other hand, the fluid individual is one who knows that "He who eats without drink, his food is poison." A thought learned, a goal achieved, must never remain confined to its specific place and parameters; it must affect his entire person and pervade his every thought and experience.
This individual also extends the fluidity of his life to his relations with his fellows. He unites with them so that their endeavors should fuse to a cohesive whole, understanding that "If I am only for myself, what am I?"
And as water, he "flows from a high place to the lowest of places." He applies his most sublime experiences to the mundane particulars of everyday life; and he relates to every man as his equal, regardless of their moral and spiritual station.