Walls have ears.
More Chinese Proverbs:
If you can't change your fate, change your attitude.
Chinese
A man combs his hair every morning -- why not his heart?
Chinese
Too much politeness conceals deceit.
Chinese
When you have read a book for the first time, you get to know a friend; read it for a second time and you meet an old friend.
Chinese
No melon peddler cries, "Bitter melons." No wine dealer says, "Sour wine."
Chinese