In exile, the Jin prince Chong’er came to Chu, and the King of Chu gave a feast for him. The king asked how he would repay him. Chong’er answered that if he ever returned to rule Jin and their armies met on the central plain, “I will withdraw three marches before you.” (Zuo Zhuan)
In 632 BCE, now Duke Wen of Jin, he faced the Chu army and withdrew three marches, about ninety li. His adviser Zi Fan explained: “Without Chu’s kindness we would not be here. We withdraw three marches to avoid them, and that is our repayment.” Then the armies met at Chengpu. The story gave Chinese the idiom 退避三舍, to withdraw three marches.