קל"ה - הלכות נטילת ידים לסעודה ג:ב
Neglecting the mitzvah of washing one's hands before a meal is a concept of the sin of eating from the Tree of Knowledge, which encompasses all the prohibitions and sins in the Torah. From this neglect comes the grasp of the Sitra Achra/Contamination of the Snake. It is because of this neglect that Chazal said a person deserves death, a concept of, "Because on the day that you will eat from it you will surely die." But, through washing one's hands before a meal a person draws upon himself purity, as in, "the river comes forth from Eden," which is a concept of the Sea of Wisdom. Then, a person's eating corresponds to 'manna that lightens within him the radiance of Hashem's Will.'