《黄帝内经·素问·三部九候论》
岐伯说：九候的脉象，都是沉细悬绝的，为阴，冬令死于阴气极盛之夜半；如脉盛大躁动喘而疾数的，为阳，主夏令，所以死于阳气旺盛之日中；寒热交作的病，死于阴阳交会的平旦之时；热中及热病，死于日中阳极之时；病风死于傍晚阳衰之时；病水死于夜半阴极之时。
岐伯曰：九候之脉，皆沉细悬绝者为阴，主冬，故以夜半死；盛躁喘数者为阳，主夏，故以日中死。是故寒热病者，以平旦死。热中及热病者，以日中死。病风者，以日夕死。病水者，以夜半死。
Qi Bo said: The pulse images of the Nine Periods are all sunken, fine, suspended, and isolated, which means yin, and one will die at midnight when yin energy is at its peak in winter. If the pulse is strong, agitated, short of breath, and rapid, it means yang, and it will die at noon when yang energy is at its peak in summer. For diseases with both cold and heat, one will die at dawn when yin and yang meet. For those suffering from internal heat and fever, they will die at noon when yang energy is at its peak. For those suffering from wind diseases, they will die in the evening when yang energy wanes. For those suffering from water diseases, they will die at midnight when yin energy is at its peak.