Can somebody please explain this?

Maybe I am missing something in the translation.

Ешь пирог с грибами, а язык держи за зубами.
Eat a pie with mushrooms, and hold your tongue behind your teeth.

Eat pie with mushrooms, but keep your tongue behind your teeth.

Thanks,
But is there any hidden meaning?

http://www.russianlife.net/pdf/SR0502.pdf

The last paragraph there answers your question. It says it's a proverb from the Stalin era, which roughly means "Hear much, speak little".

Thanks Darobat.
You are very good at finding things.