《汉书·志·天文志》
当出现而未出现，不当隐没而隐没，天下息兵，军兵在境外，则入境。
当出不出，未当入而入，天下偃兵，兵在外，入。
When it appears but does not appear, and does not disappear since it should disappear, the world will rest and its army will be abroad, then it will enter the country.