《资治通鉴·周纪·周纪四》
大王如果不向世仇韩、魏去借道，势必只有攻随水的西边，那里都是广川、大河、山林、深谷，不毛之地，大王徒有征服楚国的名义而没有得到土地的实际利益，而且大王进攻楚国时，四国必然全部起兵响应大王，当秦国、楚国军队打得难解难分时，魏国就会趁机出兵进攻留、方与？
王若不借路于仇雠之韩、魏，必攻随水右壤，此皆广川、大水、山林、溪谷，不食之地。是王有毁楚之名而无得地之实也。且王攻楚之日，四国必悉起兵以应王。
If your majesty don't borrow the passage from our mortal enemies Han and Wei, you have no choice but to attack the west of Sui River, where there are all vast plains, big rivers, forests, deep valleys, and barren lands. Your majesty will only have the name of conquering Chu but won't actually get the land. In addition, when your majesty attacks Chu, all four countries will definitely respond to the call and send troops. When the armies of Qin and Chu are in a stalemate, Wei will seize the opportunity to send troops to attack Liu and Fangyu.