Tao Te Ching 27

The skillful traveler leaves no traces of his wheels or footsteps; the skillful speaker says nothing that can be found fault with or blamed; the skillful reckoner uses no tallies; the skillful closer needs no bolts or bars, while to open what he has shut will be impossible; the skillful binder uses no strings or knots, while to unloose what he has bound will be impossible. 

In the same way the sage is always skillful at saving men, and so he does not cast away any man; he is always skillful at saving things, and so he does not cast away anything. This is called 'Hiding the light of his procedure.'

Therefore the man of skill is a master to be looked up to by him who has not the skill; and he who has not the skill is the helper of the reputation of him who has the skill. If the one did not honor his master, and the other did not rejoice in his helper, an observer, though intelligent, might greatly err about them. This is called 'The utmost degree of mystery.'