Tao Te Ching: Chapter 24
The skilful traveller leaves no traces of his wheels or footsteps; the skilful speaker says nothing that can be found fault with or blamed; the skilful reckoner uses no tallies; the skilful closer needs no bolts or bars, while to open what he has shut will be impossible; the skilful binder uses no strings or knots, while to unloose what he has bound will be impossible. In the same way the sage is always skilful at saving men, and so he does not cast away any man; he is always skilful 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 honour 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.'