During the Tang Dynasty, a scholar named Li Yifu from Yongtai (modern Yanting County, Sichuan) came from a humble family but excelled in his studies and writing. During Emperor Taizong's reign, he passed the imperial exams with a brilliant policy response and was appointed to a minor official post.
Li Yifu's greatest skill was flattery. One day, he wrote an essay that appeared to admonish the royal family but was actually a string of praises. Crown Prince Li Zhi read it and was deeply impressed, recommending it to Emperor Taizong. As a reward, Li Yifu was granted forty bolts of silk.
In 649 AD, Emperor Taizong passed away, and his son Li Zhi ascended the throne as Emperor Gaozong of Tang. Li Yifu, a favorite of Gaozong, was promptly promoted. From then on, he always wore a three-part smile, flattering Gaozong in every way. Six years later, when Gaozong sought to make his father's former concubine Wu Zetian his empress, Li Yifu strongly supported the move. As a reward, he was immediately elevated to Zhongshu Shilang and Canzhi Zhengshi, becoming the head of the Secretariat. Soon after, he was reassigned as the Right Chancellor, truly soaring to great heights.
Li Yifu appeared outwardly gentle and respectful, always smiling when speaking with others, but his colleagues knew he was a man who hid a dagger behind his smile—narrow-minded and treacherous at heart. Anyone who offended him or failed to follow his wishes would face his venomous persecution. For this reason, they secretly nicknamed him "the smiling blade."
Once, when he learned that the Supreme Court prison held a death-row female inmate of exceptional beauty, he hatched a wicked scheme to possess her. Defying national law, he ordered a prison official named Bi Zheng to pardon her. The moment she was released, he seized and took her for himself.
When the chief official of the Supreme Court discovered this, he reported the matter to Emperor Gaozong. Upon hearing the news, Bi Zhengzhi, knowing that releasing a death-row prisoner would mean his own execution, was so terrified that he hanged himself. Li Yifu had initially feared he would face severe punishment once the case came to light, but after learning of Bi Zhengzhi's suicide, he believed there would be no evidence left to convict him and thus dismissed the matter from his mind.
Wang Yifang, an imperial censor tasked with oversight, was outraged that Li Yifu, a master of the "hidden dagger behind a smile," was evading justice for his crimes. He reported to Emperor Gaozong that Li Yifu was the mastermind behind a corrupt scheme. However, Gaozong, charmed by Li Yifu's deceitful demeanor, not only refused to investigate but also demoted Wang Yifang to a minor post in the provinces.
As soon as they left the court, Li Yifu gave a fake smile and said to Wang Yifang, "Censor Wang, aren't you ashamed for trying to bring me down?" Wang Yifang replied with righteous indignation, "As a censor, I would be ashamed if I couldn't rid the court of treacherous officials!"
After this, Li Yifu grew bolder in his corruption. He gathered cronies, cultivated confidants, and had his relatives extort money and rig lawsuits, so that many flocked to his home bearing bribes, begging him to handle all sorts of illegal affairs. Li Yifu would always smile warmly while shamelessly bending the law for personal gain.
One day, he saw an unpublished appointment list in the palace and immediately saw it as a chance to extort money, memorizing the names. After returning home, Li Yifu had his son summon someone on the list and said privately, "Don't you want an official post? The decree will be issued within days!"
The man, believing Li Yifu had pulled strings for him, sent Li and his son 700 strings of cash as thanks. Days later, when the imperial decree was issued and the man indeed got the post, Li Yifu pocketed the bribe without a second thought.
Unexpectedly, a minister opposing Li Yifu uncovered this and secretly reported to Emperor Gaozong, stating, "Li Yifu has taken bribes, violated the law, leaked court secrets, and sold Your Majesty's favor for profit—he deserves severe punishment." Enraged, Gaozong issued an edict exiling Li Yifu and his son to Xizhou (in present-day Sichuan).
Li Yifu, who had long hidden a dagger behind his smile, committed countless evils and finally could not escape the net of justice—he was sentenced to exile. Civil and military officials at court all clapped their hands in joy and relief.
In 666 AD, Emperor Gaozong of the Tang Dynasty declared a grand amnesty across the empire. The 52-year-old Li Yifu, a disgraced former chancellor, believed his chance to return to power had arrived. However, upon inquiring, he learned that those sentenced to exile were still forbidden from re-entering the capital. That same year, consumed by despair, he fell ill and died.
The idiom "hiding a dagger behind a smile" is derived from this story, used by later generations to describe someone who appears kind on the surface but is treacherous and vicious at heart.
Source: *New Book of Tang*, "Biography of Li Yifu"
Meaning of the Idiom: Later, the Chinese idiom "笑里藏刀" came to describe how someone who appears kind on the surface but is treacherous and vicious at heart.