Attested in Yuan-dynasty playwright Wang Ziyi's (
王子一) 《
误入桃源》:
长江后浪推前浪,
花呵早则一片西飞一片东 — 'On the Yangtze the back waves push the front, flowers fly this way and that.' Often extended with
世上新人赶旧人 ('in the world, new people overtake the old'). Used encouragingly about generational change.