With the assistance of Yi Yin, Tang successfully overthrew the Xia Dynasty and established the Shang Dynasty. In the early days of the Shang Dynasty, everything was in need of rebuilding, and with Yi Yin's help, Tang perfected various laws and institutions, quickly restoring social order and putting the dynasty on the right track. Tang ruled for thirty years, and on his deathbed, due to his deep trust in Yi Yin, he entrusted him with the crucial responsibility of assisting the succeeding ruler.
During the Shang Dynasty, the rule of succession was that when an elder brother died, the younger brother would inherit the throne; only if there were no younger brothers would the son inherit. Shang Tang had no younger brothers, so his eldest son, Tai Ding, was supposed to succeed him. However, Tai Ding died while Tang was still alive, so according to ritual law, Tai Ding's younger brother, Wai Bing, should inherit the throne. Thus, Yi Yin supported Wai Bing to ascend the throne. Wai Bing reigned for only three years before dying, and his younger brother, Zhong Ren, succeeded him. Zhong Ren was frail and sickly, destined to be a short-lived ruler, and died of illness after four years on the throne. At this point, the only eligible heir was Shang Tang's grandson and Tai Ding's son, Tai Jia. Tai Jia was only ten years old at the time, but Yi Yin did not hesitate to support the young Tai Jia onto the throne of the Shang Dynasty. Yi Yin himself held great power, diligently assisting from the sidelines, teaching Tai Jia how to distinguish right from wrong and how to govern the state, hoping to mold Tai Jia into a virtuous ruler.
Tai Jia was young and inexperienced, and at first he could follow Yi Yin's teachings, speaking cautiously and acting prudently, adhering to the ancestral rites, and handling state affairs seriously. However, having ascended to the pinnacle of power at such a tender age, growing up surrounded by flattery, and having lost his father early without strict discipline, his unruly nature began to emerge after just a few years. Believing himself to be the sovereign above all, with no one able to control him, he gradually became complacent and grew impatient with Yi Yin's guidance. He felt that although Yi Yin was the prime minister, he was of slave origin, so why should he listen to his lessons? Thus, when Yi Yin taught him about ancestral traditions, passed down the laws established by Tang, and educated him with stories of wise rulers from history, he refused to listen and even showed hostility. Over time, he became willful, indulging in music and drink, repeatedly breaking the rites. More frighteningly, he increasingly resembled Xia Jie, abusing labor, being cruel and fond of killing, causing the people to suffer unbearably and their resentment toward him to deepen.
Regarding Tai Jia's lack of desire for self-improvement and his tyrannical nature, Yi Yin and the ministers were deeply worried, repeatedly admonishing and reminding Tai Jia that as a monarch, there were things he should and should not do. However, Tai Jia completely ignored Yi Yin's advice, not only persisting in his own willful ways but even becoming more extreme. Yi Yin was very concerned, fearing that if they continued to indulge Tai Jia's reckless behavior, the kingdom that Tang had fought so hard to establish would be ruined by him.
For the sake of the Shang Dynasty's realm and to mold Tai Jia into a wise ruler, Yi Yin decided to administer a harsh remedy to Tai Jia. It happened to be approaching the anniversary of Tang's death, and according to tradition, the sovereign was required to lead the entire court in a grand sacrificial ceremony. Tai Jia, being fond of pleasure, had no desire to preside over such a rigid and tedious ritual, but Yi Yin repeatedly stressed that as Tang's descendant who inherited the kingdom Tang had built, this duty was unavoidable unless he no longer wished to be the ruler. Reluctantly, Tai Jia took on the task and led the ministers to Tang's tomb, the Tong Palace. As the ceremony began, Yi Yin read the eulogy, declaring to Tang's spirit that for the Shang Dynasty to endure for generations, the young sovereign would be kept at Tong Palace to reflect on his conduct and learn the principles of governance. Upon hearing the eulogy, Tai Jia realized he was to be confined at Tong Palace for instruction and panicked, but with all the ministers present and clearly supporting Yi Yin's decision, he had no way out and had to comply.
Tai Jia took up residence in Tong Palace, but state affairs could not be left unattended, so Yi Yin acted as regent, governing the kingdom and performing the duties of the Son of Heaven on his behalf. To guide Tai Jia toward improvement, Yi Yin wrote three instructional texts: "Yi Xun," "Si Ming," and "Zu Hou." In "Yi Xun," he stated that corruption, debauchery, and rebellious chaos are the roots of family ruin and national disorder, and that a ruler seeking long-term stability for his country must cultivate his character and heed the advice of wise ministers. "Si Ming" explained methods for distinguishing right from wrong, clearly outlining what should and should not be done. "Zu Hou" focused specifically on the laws and systems of Shang Tang's era, teaching that the ancestral rules must not be broken, and that one should not abandon ancestral teachings or act recklessly for the sake of momentary pleasure.
Tong Palace was located far outside the Shang Dynasty capital, and although it was the tomb of Tang, the founding king of the Shang, it was extremely simple, no different from an ordinary person's grave, with only a low and small hall for annual memorial ceremonies. Taijia, a man accustomed to pleasure, could hardly bear to stay and suffer there. To help Taijia sincerely repent, Yi Yin spoke to him earnestly: "I am advanced in years and have no ambition to seize power or the throne, but the late king entrusted me with the care of his young heir on his deathbed, placing a heavy responsibility on my shoulders. To not betray the late king's trust, I cannot simply let you do as you please. You are still the ruler of the Shang, but before you govern, you must learn more, follow the right path, cultivate your character, and improve your ability to manage the state and bring peace. Therefore, take this opportunity to study here how to become a wise and enlightened king."
Tai Jia realized that this matter was beyond redemption, and coupled with the words of Yi Yin that stirred some emotions within him, he ceased his resistance and agreed to obediently stay in Tong Palace to study. There, without soft beds or fine clothes, far from the crowds of attendants and lavish pleasures, and removed from all temptations, he spent his days and nights guarding his grandfather Shang Tang's tomb, reading the admonitions Yi Yin had written for him, living a simple life—and to his surprise, his heart gradually grew calm.
Tai Jia gradually came to understand how his grandfather had endured great hardships to establish the Shang Dynasty, cultivating virtue through frugality and establishing moral character through benevolence. He sincerely admired his grandfather, and then reflected on his own lack of contribution to the state—how he had ascended the throne without thinking of governance, only indulging in pleasure and treating the people cruelly—and felt deeply ashamed. At the same time, he thought of Yi Yin’s painstaking guidance, which he had failed to comprehend, and was filled with regret. Thus, Tai Jia resolved to study diligently, to become a wise ruler worthy of his grandfather’s legacy, learning the virtues and knowledge necessary for ruling and governing, mastering the laws of the state, and understanding how to deal with the nation’s difficulties.
Thus, through continuous learning and repentance, Tai Jia lived in Tong Palace for three years. During these three years, Tai Jia truly transformed himself—he studied diligently, emulated his grandfather, held himself to strict standards, and especially focused on cultivating his moral character. Yi Yin frequently sent virtuous and talented individuals to teach him while also keeping track of his progress in Tong Palace. After thorough observation, Yi Yin confirmed that Tai Jia had reformed for the better and possessed sufficient knowledge and ability to return as ruler. Therefore, Yi Yin led the civil and military officials to Tong Palace, welcomed Tai Jia back to Bo with a grand ceremony, restored him to the throne to govern, and only assisted him from the sidelines.
After three years of transformation, Tai Jia, upon returning to the throne, completely reformed his former unruly nature. Although still young, he became mature and steady, never slacking in handling state affairs. He promoted the virtuous governance of Shang Tang, practiced diligence and frugality, and cared for the people, always acting for the greater good without violating ancestral traditions or court laws. Under his and Yi Yin's rule, the Shang Dynasty enjoyed social stability, the people lived in peace, and the feudal lords submitted, ushering in a period of stable development and prosperity. The "Records of the Grand Historian: Annals of Yin" states that after Tai Jia's restoration, "the feudal lords all returned to Yin, and the people found peace." Thus, Tai Jia earned the respect of both officials and the common people and was posthumously honored as "Tai Zong." Yi Yin also composed three chapters of "Instructions of Tai Jia" to praise Tai Jia's virtuous governance.
However, during Tai Jia's reign, it was still Yi Yin who played a decisive role in national affairs, and it was not until eight years after Tai Jia's son Wo Ding succeeded the throne that Yi Yin passed away. It is said that when he died, a great fog descended from the sky and did not disperse for three days. Wo Ding, deeply grateful for Yi Yin's devoted service to the Shang Dynasty, personally presided over his funeral, buried him with the rites befitting a Son of Heaven, and laid him to rest in the outskirts of the capital Bo.
Yi Yin was not only a founding hero who assisted Tang in conquering the realm, but also a true "veteran of five reigns." With his extraordinary talent and loyalty, he laid a solid foundation for the Shang Dynasty's six-hundred-year rule, earning him the title of the earliest virtuous prime minister and sage in Chinese history, historically known as the "Primordial Sage." According to oracle bone inscriptions, Yi Yin was ranked first among the "old and venerable ministers," receiving grand sacrifices, and was even worshipped alongside Tang, with offerings made to him alone.