There is only one commandment that prohibits a thought, and it is this: "Do Not Covet." Why does the Bible, which is preoccupied with behavior, legislate a thought? Because to covet, to want what belongs to someone else, is the root of the preceding four commandments and often leads to evil. Before someone murders, steals, lies, or commits adultery, the desire to take what is rightly someone else's usually comes first.