Tao Te Ching 27 · 27

善行無轍迹，善言無瑕謫；善計不用籌策；善閉無關揵而不可開，善結無繩約而不可解。是以聖人常善救人，故無棄人；常善救物，故無棄物，是謂襲明。故善人者不善人之師；不善人者善人之資。不貴其師，不愛其資，雖智大迷，是謂要妙。

Good conduct leaves no tracks; good speech leaves no flaw to blame; good counting does not use tally sticks; good shutting uses no bolt or bar, yet no one can open it; good tying uses no cord, yet no one can untie it. So the sage is always good at saving people, and so no one is cast away; always good at saving things, and so no thing is cast away. This is called carrying on the light. So the good man is the bad man’s teacher; the bad man is the good man’s material. Not to prize one’s teacher, not to love one’s material: though clever, one is greatly lost. This is called the essential mystery.