《伤寒论·辨霍乱病脉证并治》
经过六天，邪气行至下一经，此时病人稍能进食，为胃气稍复。再过六天，邪气又经过一经，此时病人已能够进食，示邪气行经尽、邪气衰尽、胃气恢复，那么再过一天，即十三天，疾病就会痊愈。
欲似大便而反矢气，仍不利者，属阳明也，便必硬，十三日愈，所以然者，经尽故也。下利后，当便硬，硬则能食者愈；今反不能食，到后经中，颇能食，复过一经能食，过之一日，当愈。
After six days, the evil qi has traveled to the next meridian, and at this time the patient can eat a little, indicating that the stomach qi has recovered a little. After another six days, the evil qi has passed through another meridian, and at this time the patient can already eat, indicating that the evil qi has passed through the meridian, the evil qi is exhausted, and the stomach qi has recovered, then in another day, that is, thirteen days, the disease will be cured.