During the Spring and Autumn period, Duke Xiang of Qi, after allying with four other states to attack Wei and suffering a defeat, feared retaliation from King Zhuang of Zhou. He dispatched Lian Cheng as general and Guan Zhifu as deputy to guard Kui. Reluctant but bound by duty, they carefully asked the duke before departing, "This border duty is arduous, and we dare not refuse. But when will you send someone to relieve us?"
Duke Xiang was eating a melon and casually replied, "Replace them when the melons ripen." He meant: you set out when the melons ripen this year, and when they ripen next year, I will send someone to relieve you.
The following summer, when the melons ripened, Lian Cheng and Guan Zhifu recalled Duke Xiang of Qi's promise to replace them "when the melons ripen." They sent someone to the capital Linzi to investigate whether the duke intended to send replacements. The scout returned, reporting that the duke was not in Linzi but had been in Gucheng for over a month, with no word of any replacement. Lian Cheng, unable to contain his fury, wanted to kill the duke. But Guan Zhifu, more patient, advised against violence, suggesting instead, "Let's send melons as a gift to the duke, gently reminding him that 'melon season' has arrived, hoping he'll keep his word. If that fails, we can act. Courtesy before force!"
They did as instructed. However, Duke Xiang flew into a rage instead, saying, "Whether to replace or recall is for me to decide—how dare you request it yourself? Wait until the next melons ripen!"
When Generals Lian and Guan heard this reply, they were furious at Duke Xiang's treachery and led their troops back to Linzi, where they killed him.
Later, the idiom "Replace at the Melon Season" came to describe completing a term of office and being succeeded by a replacement.
Source: *Zuo Zhuan*, "Duke Zhuang of Lu, Year 8"
Meaning of the Idiom: Later, the Chinese idiom "及瓜而代" came to describe completing a term of office and being succeeded by a replacement.