31. Was Panætius or Aristotle, who also wrote on duty, earlier than David? Why, Pythagoras himself, who lived before the time of Socrates, followed the prophet David’s steps and gave his disciples a law of silence. He went so far as to restrain his disciples from the use of speech for five years. David, on the other hand, gave his law, not with a view to impair the gift of nature, but to teach us to take heed to the words we utter. Pythagoras again made his rule, that he might teach men to speak by not speaking. But David made his, so that by speaking we might learn the more how to speak. How can there be instruction without exercise, or advance without practice?