《淮南子·泰族训》
水性柔和而清澈，那些幽谷中不流动的积水会长满青苔，这是因为没有疏理水的本性而造成的。
水之性，淖以清，穷谷之污，生以青苔，不治其性也。
Water’s nature is gentle and clear, while the stagnant water in ravines grows moss, which is caused by the water’s nature not being cleared.