背后胡言那是狗当面骂醒那是友
[bèi hòu hú yán nèi shì gŏu dāng miàn mà xĭng nèi shì yŏu]
Means 'idle talk behind backs comes from foes; honest rebukes face-to-face come from friends.' It critiques hypocrisy, emphasizing trust in genuine criticism over hidden malice.