《太平广记·卷四百五十一·狐五》
又过了十多天，不得已，有事要办必须启程，走到外城的大门时，郑氏忽然说肚子疼，下了马就跑，速度快得象风一样。
又十余日，不获已，事理须去。行至郭门，忽言腹痛，下马便走，势疾如风。
More than ten days later, he had no choice but to leave because of business. When he reached the gate of the outer city, Zheng suddenly said that she had a stomachache, got off the horse and ran, as fast as the wind.