watch your mouth
US /wɑtʃ jʊər maʊθ/
UK /wɑtʃ jʊər maʊθ/

1.
a warning to someone to stop using offensive or inappropriate language
:
•
Hey, watch your mouth! There are children present.
•
If you don't watch your mouth, you'll get into trouble.
a warning to someone to stop using offensive or inappropriate language