It's wrong to hold on to something that isn't yours
Jerry has borrowed Marty's lawn mower and Marty is asking for it back.
Jerry wants to be able to mow his lawn regularly.
Jerry returns the lawn mower and finds a used one for a low price.
Jerry continues to use Marty's lawnmower and does not return it after being asked multiple times.
Jerry can now mow the lawn without needing to borrow from friends.
Marty gets fed up and takes Jerry to small claims court.