It's wrong to take other people's property.
Homer has a neighbor Ned who he often borrows things from.
Homer wants a riding lawn mower.
Homer borrows Neds mower once, asks where he got it and buys one for himself.
Homer takes the riding lawn mower from Neds yard and will not give it back.
Homer now mows his lawn in a quicker and more enjoyable way.
Ned calls the police and presses charges resuling in Homer being arrested for theft.