《黄帝内经·素问·疟论》
岐伯说：这是由于阴阳上下相争，虚实交替而作，阴阳虚实相互移易转化的关系。
岐伯曰：阴阳上下交争，虚实更作，阴阳相移也。
Qi Bo said: This is a result of the mutual strife between yin and yang and the alternating movements of deficiency and excess. That is, yin and yang and deficiency and excess mutually transform and change.