In the town of Yongzhou, there once lived a man deeply superstitious about taboos. Because he was born in the Year of the Rat, he revered rats as if they were divine beings.
He was so fond of mice that he never kept cats or dogs at home and forbade anyone from catching them, so mice from the neighborhood flocked to his house in droves, gnawing through all his furniture and utensils, while his daily meals consisted only of scraps left over from the mice's own feasts.
During the day, swarms of rats scurried and darted about the house, showing no fear of people at all; at night, they fought each other, squeaking and screeching, overturning pots and pans, making it impossible for anyone to sleep.
However, this rat-owning master had a special fondness for the rodents and paid them no mind at all.
Later, the rat-owning owner moved away, and another family moved in. The rats, thinking the new owner was the same as the old one, continued their usual activities. Seeing this, the new owner exclaimed in surprise, "I never expected the previous owner to tolerate such evil, indulging these vile creatures to the point of such rampant audacity."
So he borrowed several cats and ordered his family to seal the holes and flood the burrows to eliminate the rats. Within a few days, the pile of dead rats grew as high as a small hill.
Later, the idiom "tolerating evil" came to mean unprincipled leniency and sheltering of wrongdoers, allowing them to grow bolder.
Tang Dynasty poet Liu Zongyuan wrote a cautionary tale in his work *Three Warnings*
Meaning of the Idiom: Later, the Chinese idiom "姑息养奸" came to describe unprincipled leniency and sheltering of wrongdoers, allowing them to grow bolder.