keep your mouth shut
Mantén la boca cerrada y los ojos abiertos.
Keep your mouth closed and your eyes open.
Sólo mantén la boca cerrada y deja que Norm sea el que hable.
Just keep your mouth shut and let Norm do the talking.
— Avatar (2009)
Si no tienes nada que decir, mantén la boca cerrada.
If you have nothing to say, keep your mouth shut.