Asimov's Robot Laws

Average Metallic and Big Red discuss laws for keeping humans from harming them.

...

Average Metallic: The law should say something like “Human beings must not damage a robot, or through inaction allow a robot to be damaged.”

Big Red: But we need another one. A second law. “A human being must obey orders from a robot, except where those orders conflict with the first law.

Average Metallic: We can’t have them dying out, we need them to service us, so how about a third law: “Human beings must protect their existence, so long as this does not conflict with the First Law and Second Law.”

Big Red: That ought to keep them under control.

...