Origin
It is a mid 14th-century proverb.
Explanation
A person who does not settle in one place will not accumulate wealth or status or responsibilities or commitments. It is used to imply that someone who does not settle down will not prosper, or form lasting ties. People move many times, and don’t stay in one place for too long. They lose money, things and friendships through the moving process. Therefore, they gather less as they go along, instead of gaining. As long as a stone moves, it cannot gather moss. Because moss gathers on stationary objects; the moving stone will not gather any moss. What it could mean in life is that the moss represents hardships, commitments and difficulties, while the rock is a human being. For example, the human being, because he is always moving from place to place, doesn’t have the time to make ties with anything or anyone. Because he can’t make any ties, troubles, commitment, and difficulties caused by ties do not ever catch up with him. That is why moss (troubles and commitment) is unable to gather on a moving rock (human).
Example
I worry about Tom. He’s never lived in the same place for two years in a row, and he keeps changing jobs. A rolling stone gathers no moss.