In the Eastern Han Dynasty (东汉), there was a man named Chen Shi (陈寔) .
One day, a thief slippedinto his living-room. Hiding behind the beam, the thief waited for Chen Shi to fall asleep.
Chen Shi, finding the thief, called his family together, saying, "To be a uprightman one must have aspirations. Men are not born evil. But if one gets used to doing evil things, it will be hard to reform. The gentleman above the beamis such a man."
The thief, hearing this, hurriedlyjumped down and knelt on the ground to beg forgiveness.
This idiom is used to refer to a thief.