《礼记·学记》
鼓的声音并不相当于五声中的哪一声，但是当乐器演奏时，没有鼓则五声就没有和谐的节奏；水的颜色并不相当于五色中的哪一色，但是当绘画的时候，没有水则五色就不鲜明；有学问并不等于就可以做官，可是做官的如果没有学问就做不好工作；老师并不相当于五服中的哪一种亲属，但是五服之亲如果没有老师的教诲，则他们之间的感情就不亲密。
鼓无当于五声，五声弗得不和。水无当于五色，五色弗得不章。学无当于五官。五官弗得不治。师无当于五服，五服弗得不亲。
The sound of a drum is not equivalent to any of the five tones, but when playing a musical instrument, if there is no drum, then the five tones will not have harmonious rhythm; the color of water is not equivalent to any of the five colors, but when painting, if there is no water, then the five colors will not be distinct; being learned does not mean that one can become an official, but if an official is not learned, then he will not be able to do his job well; a teacher is not equivalent to any of the five relatives, but if the five relatives do not receive the teachings of a teacher, then their relationship will not be affectionate.