Emperor Xuanzong of the Tang Dynasty, following the example of Emperor Taizong, appointed virtuous ministers and worked diligently to govern, ushering in the renowned "Kaiyuan Golden Age." However, after reigning peacefully for over twenty years, he grew complacent, gradually indulging in pleasure and neglecting state affairs.
Li Linfu, the Vice Minister of the Ministry of Personnel, was an unlearned and incompetent man who, despite lacking real ability, was highly skilled at flattery and sycophancy. By colluding with eunuchs and currying favor with imperial concubines, he kept himself informed of everything happening within the palace. He managed to learn every detail of Emperor Xuanzong of Tang's words and actions in the court, so whenever the emperor consulted him on matters, he could always respond in a way that aligned perfectly with the emperor's thoughts. Moreover, he frequently flattered Emperor Xuanzong in his memorials, which made the emperor grow increasingly fond of him.
At that time, Yang Guifei had not yet entered the palace, and Emperor Xuanzong of Tang was deeply infatuated with Consort Wu Huifei. Prince Shou was Consort Wu's son, so he was greatly favored by Emperor Xuanzong, while the crown prince and other imperial sons gradually fell out of favor. Seeing Consort Wu's influence, Li Linfu bribed eunuchs in the palace to curry favor with her, and he assured her that he would do everything in his power to protect Prince Shou. Consort Wu was very pleased with him, so she often mentioned him in front of Emperor Xuanzong and spoke highly of him.
At that time, Prime Minister Zhang Jiuling was a very upright official who often advised Emperor Xuanzong of Tang not to become complacent or indulge in comfort after achieving some success. When Emperor Xuanzong wanted to appoint Li Linfu as prime minister, he consulted Zhang Jiuling about it. Knowing that Li Linfu was both talentless and morally unfit for the position, Zhang Jiuling bluntly told Emperor Xuanzong: "The prime minister is a key state official with immense responsibilities that affect the nation's security. Li Linfu is an unlearned and incompetent person. If Your Majesty appoints him as prime minister, the country will face great danger."
Li Linfu soon learned of this matter and was extremely furious, wishing he could tear Zhang Jiuling into a thousand pieces. After calming down, he became determined to eliminate Zhang Jiuling, realizing that as long as Zhang Jiuling remained, he could never become prime minister. Thus, he began to seize every opportunity to slander Zhang Jiuling.
Emperor Xuanzong of Tang intended to promote the Shuofang general Niu Xianke, but Zhang Jiuling argued that although Niu Xianke was highly skilled in financial management, he had no education whatsoever and should not be given an important post. Li Linfu, having discerned the emperor's intentions, said to him, "Niu Xianke is a man of great talent and the ideal candidate for prime minister. Zhang Jiuling is out of touch with the times and is utterly unfit to serve as prime minister." Shortly after, Emperor Xuanzong again discussed the promotion of Niu Xianke with Zhang Jiuling. Zhang Jiuling persisted in his view and opposed the promotion. The emperor suddenly flew into a rage and shouted, "I am the sovereign of this nation. I can promote whomever I wish, and you have no say in it!"
In 736 AD, Wang Yuandan, the governor of Weizhou, was investigated by the imperial court for corruption. Wang Yuandan's wife was the former wife of Yan Tingzhi. Yan Tingzhi, still holding onto old feelings, planned to clear Wang Yuandan's name to ensure his ex-wife's safety. This matter quickly reached the ears of Li Linfu, who knew that Zhang Jiuling and Yan Tingzhi were very close friends. If Yan Tingzhi were to be prosecuted, Zhang Jiuling would surely step forward to defend him. So, Li Linfu secretly reported the matter to Emperor Xuanzong of Tang. Things unfolded exactly as Li Linfu had predicted: Emperor Xuanzong investigated Yan Tingzhi for harboring a criminal, and upon hearing this, Zhang Jiuling vigorously defended Yan Tingzhi. Seizing this opportunity, Li Linfu accused Zhang Jiuling of forming a faction with Yan Tingzhi and Pei Yaoqing for personal gain. Emperor Xuanzong, who already disliked Zhang Jiuling, dismissed him from his position as prime minister and promoted Li Linfu to take his place.
After Li Linfu became Prime Minister, in order to monopolize power, he always surrounded himself with those who lacked independent judgment and were compliant. He recommended Niu Xianke as Left Chancellor, who never interfered in government affairs, leaving all matters to Li Linfu alone. After Niu Xianke's death, Minister of Justice Li Shizhi was appointed Left Chancellor by Emperor Xuanzong of Tang. Li Shizhi was also fond of power and intended to contend with Li Linfu, but ended up being persecuted by him. Subsequently, Li Linfu recommended the indecisive Chen Xilie as Left Chancellor, while all state power remained firmly in Li Linfu's hands.
Li Linfu also isolated the court officials from Emperor Xuanzong of Tang, preventing them from offering advice to the emperor. He even openly told the imperial censors, "Our emperor is extremely wise, and his decrees are always correct. As his subjects, we only need to follow his orders. There is no need for you to debate his commands. You have all seen the ceremonial horses in front of the palace! They are fed very expensive fodder, equal to the treatment of third-rank officials, but if any horse dares to neigh, it is immediately killed, with no chance to regret it." The censor Du Jin did not take Li Linfu's words to heart and still submitted a memorial to Emperor Xuanzong offering advice, but the next day he was demoted to a county magistrate in a remote area. From then on, all court officials feared Li Linfu, and no one dared to offer advice to Emperor Xuanzong again.
One day, Emperor Xuanzong of Tang remembered Yan Tingzhi, who was serving as a prefectural governor in a remote area, and said to Li Linfu, "Where is Yan Tingzhi now? He is a very talented man and should be given an important position at court." Li Linfu replied, "I don't know where he is either, but I can find out." Afterwards, he immediately sent for Yan Tingzhi's younger brother and said, "I know your brother is in the provinces and misses the Emperor very much, wanting to return to the capital to see him. I have an excellent plan to help him fulfill this wish." Yan Tingzhi's brother was overjoyed and immediately asked Li Linfu what to do. Li Linfu said, "It's simple! Tell your brother to submit a memorial claiming he is ill and needs to return to the capital for treatment." Yan Tingzhi's brother thought this was a great idea and quickly wrote a letter to his brother. Yan Tingzhi indeed followed Li Linfu's advice and submitted a memorial to Emperor Xuanzong. After receiving the memorial, Li Linfu told the Emperor, "Yan Tingzhi is now seriously ill and can no longer serve Your Majesty. What a pity!" Hearing this, Emperor Xuanzong had to give up the idea of promoting Yan Tingzhi. In 747 AD, during the imperial examinations, Li Linfu, fearing that talented individuals who passed would threaten his position, used his power to ensure that no one in the entire empire was admitted. He even deceived Emperor Xuanzong by claiming that all the worthy and capable people in the world were already serving by his side. Li Linfu not only prevented the Emperor from appointing new talent but also slandered and pushed out prominent court officials, making all civil and military officials submit to his authority. By constantly flattering and catering to Emperor Xuanzong's wishes, Li Linfu gained the Emperor's favor and served as Prime Minister for nineteen consecutive years during Xuanzong's reign, plunging the Tang Dynasty into political darkness and deepening social conflicts.
Li Linfu, when interacting with others, always appeared outwardly friendly, speaking sweet and kind words, but in reality, he was a cunning and treacherous person who often devised malicious schemes to harm others, completely opposite to his surface demeanor. Over time, people saw through his true nature and said behind his back that he had "honey in his mouth but a sword in his belly," which is precisely the origin of the idiom "honey-mouthed, dagger-hearted."