St. Isaac of Syria died ca. 700

Silence is a mystery of the age to come, but words are instruments of this world. A faster endeavors to liken his soul to the nature of spiritual beings. Through silence and continual fasting a man sets himself apart so as to perservere in his divine labor within his hidden self. In these very mysteries the invisible hosts perform the liturgy that is filled with divine mysteries and the holiness of the Supreme Being Who rules the ages. Some of the saints set themselves apart in order to enter into the mysteries of God and were marked by this seal; some were entrusted with the governance of a strong people; others were entrusted to receive authority over the elements and by a great wonder the natures of created things were obedient to the command of their words; and some of them were entrusted to reveal hidden things, concealed in the secret silence of the Lord, for the renewing of those who are in the middle state. Indeed, it would not have been fitting that such mysteries should be administered by men whose belly is full and whose intellect is confused because of intemperance. The saints, however, did not dare to converse with God or raise themselves toward His hidden mysteries, unless their limbs were weak, their color pale by reason of gnawing hunger, and their intellect quiet in its perceptivity through renunciation of every earthly thought. (The Ascetical Homilies, Homily 65)