Tao Te Ching Chapter 27
A good runner leaves no track.
A good speech leaves no flaws for attack.
A good reckoner makes use of no counters.
A well-shut door makes use of no bolts,
And yet cannot be opened.
A well-tied knot makes use of no rope,
And yet cannot be untied.
Therefore the Sage is good at helping men;
For that reason there is no rejected (useless) person.
He is good at saving things;
For that reason there is nothing rejected.
- This is called stealing the Light.
Therefore the good man is the Teacher of the bad.
And the bad man is the lesson of the good.
He who neither values his teacher
Nor loves the lesson
Is one gone far astray,
Though he be learned.
- Such is the subtle secret.