In the Spring and Autumn Period, a farmer from the State of Song was working in his field when he saw a rabbit accidentally run into a tree stump and break its neck. He took the rabbit home and enjoyed a delicious meal. That night, he thought, "I don't need to work so hard. I can just wait by the stump each day for another rabbit." From then on, he abandoned his farming and simply waited by the stump for more rabbits to run into it.
This idiom satirizes those who idly wait for good luck to strike instead of working hard to achieve their goals.