流水不腐，戶樞不蠹 [ㄌㄧㄡˊ ㄕㄨㄟˇ ㄅㄨˋ ㄈㄨˇ , ㄏㄨˋ ㄕㄨ ㄅㄨˋ ㄉㄨˋ; liu2 shui3 bu4 fu3 , hu4 shu1 bu4 du4] Flowing water does not rot, nor a door-hinge rust (idiom) constant activity prevents decay ◄ ►
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