Tao Te Ching: Chapter 19
He who knows (the Tao) does not (care to) speak (about it); he who is (ever ready to) speak about it does not know it.
He (who knows it) will keep his mouth shut and close the portals (of his nostrils). He will blunt his sharp points and unravel the complications of things; he will attemper his brightness, and bring himself into agreement with the obscurity (of others). This is called 'the Mysterious Agreement.'
(Such an one) cannot be treated familiarly or distantly; he is beyond all consideration of profit or injury; of nobility or meanness:--he is the noblest man under heaven.