The Art of War by active 6th century B.C. Sunzi

and Earth, unending as the flow of rivers and streams; like the sun and moon, they end but to begin anew; like the four seasons, they pass away but to return once more. [Tu Yu and Chang Yu understand this of the permutations of _ch’i_ and _cheng_. But at present Sun Tzŭ is not speaking of _cheng_ at all, unless, indeed, we suppose with Cheng Yu-hsien that a clause relating to it has fallen out of the text. Of course, as has already been pointed out, the two are so inextricably interwoven in all military operations, that they cannot really be considered apart. Here we simply have an expression, in figurative language, of the almost infinite resource of a great leader.]