Zheng Xuan, a master of classical studies in the Eastern Han Dynasty, was a prodigy from childhood—sharp-witted and diligent, he could recite and explain Confucian texts by age twelve or thirteen. He also loved astronomy and mathematics, predicting fortunes from weather and wind patterns, and was skilled in mystical arts and essay writing. Contemporaries marveled at his rare genius, calling him a "child prodigy."
When Zheng Xuan first studied under the renowned classical scholar Ma Rong, Ma had four hundred disciples, but only fifty were permitted to attend his lectures in person. For three years, Zheng never once met Ma face-to-face, learning only from senior students—yet he never slackened, studying day and night. One day, Ma Rong was discussing divination techniques with his disciples and encountered a difficult problem. Hearing that Zheng Xuan was skilled in this art, Ma summoned him. Present also was Ma's top disciple Lu Zhi. Ma posed seven questions; Zheng immediately answered five, while Lu Zhi answered three. Ma Rong was astonished and admitted, "I am not your equal."
After completing his studies, Zheng Xuan returned to his hometown, where he both took on disciples and annotated the classics. At the time, the conflict between the New Text and Old Text schools of classical studies was fierce, with each side attacking the other. Zheng Xuan, however, synthesized both traditions, merging them into a unique system of his own. He even incorporated the prevailing theories of heavenly retribution, portents, disasters, and auspicious signs into his commentaries. Growing up in the Yan-Qi region, the birthplace of immortality cults and alchemists, Zheng Xuan was deeply influenced from childhood and firmly believed in fate. He held that life, death, wealth, honor, and misfortune were all predetermined by heaven, and that all natural phenomena arose from the interplay of yin and yang. Believing that petty men held power and that yin energy was overwhelming, he argued that gentlemen must act with caution. He himself withdrew from the world, refusing official appointments, and before any action, he would perform divination to determine its auspiciousness.
In the spring of 200 AD, the 74-year-old scholar Zheng Xuan had a dream. In it, Confucius himself appeared and said, "Rise, rise. This year is the Year of the Dragon, and next year is the Year of the Snake." Awakening, Zheng Xuan interpreted this as an omen: according to tradition, dragon and snake years were inauspicious for sages. Realizing his time was near, he soon fell ill.
At that time, Yuan Shao and Cao Cao's armies were locked in a standoff at Guandu. Yuan Shao sent for Zheng Xuan to follow his army. Reluctantly, Zheng Xuan traveled to Yuancheng (present-day Daming, Hebei) while ill, but could not go on due to his worsening condition and died there in June of that year. Later, the idiom "Year of the Dragon and Snake" came to refer to the end of one's lifespan.
Source: *Book of the Later Han*, "Biography of Zheng Xuan"
Meaning of the Idiom: Later, the Chinese idiom "岁在龙蛇" came to describe how the end of one's lifespan is referred to.