On the border between the states of Chu and Liang, both sides grew melons. The Liang people were skilled farmers, their melons large and sweet, selling out quickly at the border market. The Chu people, less adept, grew small, bland melons that went unsold as they watched the Liang farmers return home singing. Frustrated, a group of Chu men conspired and, under cover of darkness, sneaked into the Liang melon fields and destroyed many of their crops.
The next morning, the men of Liang went to their melon field and found it in utter ruin—smashed melons with bright red flesh exposed, trampled leaves, and vines torn apart. Heartbroken, they noticed some men from Chu pointing and laughing in the distance, realizing who was responsible. The neighbors gathered and plotted to return the favor by destroying the Chu melon field in turn.
When the county magistrate Song learned of this, he immediately stopped the people and forbade them from retaliating against the Chu people. Instead, he ordered the citizens of Liang to help the Chu farmers water their melons. As the Chu melons grew better and better, the Chu people felt deeply grateful.
When the King of Chu heard of this, he prepared generous gifts to thank the people of Liang and requested to form a bond with the Liang state. Because of this small act of watering melons, the two kingdoms of Liang and Chu grew increasingly friendly.
Later, the idiom "The Kindness of Watering Melons" came to describe not holding grudges over trivial matters, but repaying resentment with virtue, thereby improving relations between both sides.
Source: *New Prefaces*, "Miscellaneous Affairs" by Liu Xiang
Meaning of the Idiom: Later, the Chinese idiom "浇瓜之惠" came to describe how not holding grudges over trivial matters, but repaying resentment with virtue, thereby improving relations between both sides.