(ג) וַיְעַנְּךָ וַיַּרְעִבֶךָ וַיַּאֲכִלְךָ אֶת הַמָּן אֲשֶׁר לֹא יָדַעְתָּ וְלֹא יָדְעוּן אֲבֹתֶיךָ לְמַעַן הוֹדִעֲךָ כִּי לֹא עַל הַלֶּחֶם לְבַדּוֹ יִחְיֶה הָאָדָם כִּי עַל כָּל מוֹצָא פִי יקוק יִחְיֶה הָאָדָם.
(3) And He afflicted thee, and suffered thee to hunger, and fed thee with manna, which thou knewest not, neither did thy fathers know; that He might make thee know that man doth not live by bread only, but by every thing that proceedeth out of the mouth of the LORD doth man live.
At the core of every existence is a divine utterance that created it ("Let there be light," "Let the earth sprout forth vegetation," etc.), which remains nestled within it to continuously supply it with being and life. The soul of man descends into the trappings and trials of physical life in order to unite with and elevate the "sparks of holiness" buried in the food it eats, the clothes it wears, and all the other objects and forces of the physical existence it interacts with.
For when a person utilizes something, directly or indirectly, to serve the Creator, he penetrates its shell of mundanity, revealing and realizing its Divine essence and purpose.
Therein lies a deeper meaning to the verse (Psalms 107:5): "The hungry and the thirsty, in them does their soul wrap itself." A person may desire food and sense only his body's hunger, but in truth, his physical craving is but the expression and external "packaging" of a deeper yen -- his soul's craving for the sparks of holiness that are the object of its mission in physical life.
(Rabbi DovBer, the Maggid of Mezeritch)
This explains a most puzzling fact of life: how is it that man, the highest form of life, derives vitality and sustenance from the lower tiers of creation -- the animal, vegetable and mineral?
But the true source of nourishment is the "Divine utterance" in every creation, and, as the Kabbalists teach, the "lowlier" the creation, the loftier the divine energy it contains. In this, the universe resembles a collapsed wall, in which the highest stones fall the farthest.
(Rabbi Schneur Zalman of Liadi)