Silence, then, is a desirable thing for those who are ignorant, but for those who desire knowledge, and who have at the same time a love for their master’s freedom of speech, is a most necessary possession. Accordingly it is said, in the book of Exodus, "The Lord will fight for us, and you will be silent."
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And, immediately afterwards, there is added a scripture in the following words: "And the Lord said unto Moses, Why dost thou cry unto me?" As it is proper for those persons to be silent who can say nothing worthy of being listened to, and for those to speak who, through love of wisdom, believe in God; and not only to speak quietly but to cry out with exceeding noise, not indeed with the noise of the mouth and tongue, by means of which they say that the air is affected with a rotatory motion, and so is rendered capable of being perceived by the hearing, but by the all-instructed and very loudly speaking organ of that voice of which no mortal man is the hearer, but only the uncreated and immortal God.