St. John Climacus
“Fasting ends lust, roots our bad thoughts, frees one from evil dreams. Fasting makes for purity of prayer, an enlightened soul, a watchful mind, a deliverance from blindness. Fasting is the door of compunction, humble sighing, joyful contrition, and end to chatter, an occasion for silence, a custodian of obedience, a lightening of sleep, health of the body, an agent of dispassion, a remission of sins, the gate, indeed, the delight of Paradise.”
Source: St. John Climacus, The Ladder of Divine Ascent