Proverb meaning 'walls have ears' — be careful what you say because someone might be listening; a warning to be cautious about speaking privately.
大事な計画の話はここではやめよう。壁に耳あり障子に目ありだから。
Let's not discuss the important plan here. Walls have ears, after all.
社内の悪口は控えたほうがいい。壁に耳あり障子に目ありだよ。
You should refrain from speaking ill of colleagues in the office. Walls have ears.