无平不陂，无往不复。
No plain is not followed by a slope; no advance is not followed by return. (Translated by Fu Huisheng) / While there is no state of peace that is not liable to be disturbed, and no departure (of evil men) so that they shall not return. (Translated bybyu J. Legge) (Commonly used with reference to the relation between cause and effect of things.)
