《资治通鉴·宋纪·宋纪四》
当初，刘宋文帝派到彦之北伐出征前，就告诫他说： 如果魏国的军队有所举动，你们应该在敌人没有攻到之前，先行渡过黄河；如果他们没有动静，你们就要留守彭城，不要前进。 
初，帝之遣到彦之也，戒之曰： 若北国兵动，先其未至，径前入河；若其不动，留彭城勿进。 
Previously, when emperor Wen of Liu Song had sent Tan Daoji on his northern campaign, he had warned him, “If the Wei army takes action, you should cross the Yellow River before their army reaches you; if they don’t, then you should hold on to Pengcheng, and don’t advance.”