The source of all illness is the lovesickness of the soul. She yearns to return to her Beloved Above, and so is repulsed by the human form, her prison of pain.

Two things, then, must be repaired, and body and soul will be healed:

The human body must open itself to become a holy temple for the Infinite G‑d who desires it for His dwelling.

The soul must learn to discover the Infinite G‑d from within this human form, the place where He most desires to dwell.

Maamar Ani Hashem Rof’echa