《黄帝四经·经法·道法》
四季更迭、昼夜交替，荣枯变换、柔刚转化便是天地间所存在的固有规律。
天地之恒常，四时、晦明、生杀、輮刚。
The changing of the seasons, the alternation of day and night, the change from prosperity to decline, and the transformation from softness to hardness are the inherent laws that exist between heaven and earth.