《国语·晋语·文公救宋败楚于城濮》
我狐偃听说过，用兵作战，理直才会气壮，理曲士气就会低落。
偃也闻之：战斗，直为壮，曲为老。
I, Hu Yan, have heard that the use of troops in battle depends on righteousness to boost morale, and the lack of righteousness will lead to low morale.