Chametz and matzah are opposites.
Matzah is unpretentiously flat and plain tasting; chametz is inflated and tasty.
Matzah therefore parallels humility and self-restraint, while chametz parallels the self-importance of ego and the superficial satisfaction of self-indulgence.
The Torah therefore forbids chametz to the extreme during Passover, since one must eradicate all vestige of the evil inclination and the ego. By eradicating its dietary manifestation, we weaken its spiritual manifestation as well.
This, however, begs the question: Why is it that chametz is permitted during the rest of the year?! Furthermore, how is it that chametz is actually required during the Shavuot Temple service?
Every year, beginning with the first day of Passover we enter a “spiritual program” designed to help us leave “Egypt” and condition us to encounter G-d at Sinai, seven weeks later, on the holiday of Shavuot. During the Exodus, our spiritual lowliness was such that it was as if our backs were to G-d. Our goal for Shavuot is to align ourselves with G-d, to stand “face to face.”
Our divine sensibility needs no preparation for this encounter. It is our animalistic consciousness that is in need of transformation. Once transformed, it too can stand before G-d and receive the Torah. We can then love G-d with all our heart, with both our G-dly and selfish inclinations.
Why seven weeks? Kabbalah teaches that the animalistic consciousness possesses seven primary impulses. Left to their own devices, these impulses lead us away from our true selves. Our task is to transform these impulses and harness their passion for goodness. For example, passionate desire for material pleasures can be transformed into passionate desire to cleave to
G-d, the source of all existence. Egotistical pride can be transformed into a healthy pride borne of an awareness of one’s G-dly potential.
Hence the seven weeks between Passover and Shavuot: Each week we work on transforming one of the seven impulses.
But in order to transform the animal soul’s impulses, we must first subdue them.
During Passover, the ego must be completely and unconditionally humbled. This enables us to begin the process of transforming the ego and harnessing its power for holiness.
Chametz is therefore permitted after Passover and becomes a mitzvah during the Temple service of Shavuot. For our ultimate goal is not merely to subdue our inner “animal” but to gradually transform it so that it too can stand before G-d, face to face (Rabbi Schneur Zalman of Liadi).
—Haggadah for Passover