a lie has no legs

a lie has no legs

Because a lie has nothing to support it ("no legs" to stand on), it is unsustainable and can be easily recognized and dismissed as a lie. A: "I'm really worried that this rumor about me is going to reach the whole school." B: "No way—a lie has no legs, so the truth will definitely prevail."
See also: leg, lie, no
Farlex Dictionary of Idioms.
See also:
  • lying
  • lie like a rug
  • give the lie to
  • give the lie to (something)
  • give the lie to something
  • give the lie to, to
  • lie through (one's) teeth
  • lie through one's teeth
  • lie through teeth
  • lie through your teeth