During the late Eastern Han Dynasty, Yu Fan of Kuaiji was a learned and eloquent man appointed as merit officer by Kuaiji’s governor, Wang Lang. When Sun Ce attacked Kuaiji, Yu Fan urged Wang Lang, "Sun Ce is magnanimous and beloved by the people—do not oppose him." Wang Lang refused, was defeated, and fled. After Sun Ce took over, he kept Yu Fan as merit officer and treated him like a friend.
Later, Sun Ce planned to seize Yuzhang. Hua Xin was then serving as the Grand Administrator of Yuzhang Commandery. Sun Ce asked Yu Fan to persuade Hua Xin to surrender the city, saying, "Although Hua Xin is very famous, he is no match for me. If war breaks out, it will inevitably harm the people! Please go and make my intentions clear to him."
When Yu Fan was sent on a mission to Yuzhang, he asked Hua Xin, "I've heard you and Wang Lang are equally famous—I've long admired you from the east." Hua Xin replied, "I am not as good as Wang of Kuaiji." Yu Fan pressed, "How does Yuzhang's army compare to Kuaiji's?" Hua Xin answered, "Far inferior." Yu Fan then urged, "Sun Ce's wisdom is unmatched, his military skill divine—you must have heard how he pacified Kuaiji. Defending this isolated city against overwhelming odds, with his army approaching, if you don't decide soon, you'll regret it too late." This finally persuaded Hua Xin to surrender. Source: *Records of the Three Kingdoms*, "Biography of Hua Xin"
After Sun Ce smoothly occupied Yuzhang, he assessed merits and granted rewards, especially praising Yu Fan, saying, "You shall remain as my 'Xiao He' in the role of Merit Officer to guard Kuaiji." Later, the idiom "assess merits and grant rewards" came to mean evaluating achievements and bestowing honors.
Source: *Records of the Three Kingdoms*, "Book of Wu: Biography of Yu Fan"
Meaning of the Idiom: Later, the Chinese idiom "计功行赏" came to describe evaluating achievements and bestowing honors.