According to Zuo Zhuan's Fifteen Years of Gong Xuan, during the Spring and Autumn Period, Wu Wei had a concubine who was very fond of her, but she was barren. After Wei Wuzi was seriously ill, he said to his son Wei Ke, "After I die, let this concubine marry someone else!" Soon, Wei Wuzi was critically ill and told Wei Ke, "After I die, let this concubine die with me!" "After the death of Wei Wuzi, Wei Ke asked his concubine to marry someone else, saying," My father was sober when he first got sick; When he was dying, his mind was a little confused. I should have listened to him when he was sober! "
Later, the State of Qin attacked the State of Jin, and the armies of the two countries fought near a place called Fu Cha. Wei Ke also took part in this battle, and the enemy will be Du Hui and Qin Warriors. When Wei Ke confronted Du Hui, he found an old man, facing Du Hui's way, forming a tall and dense straw rope on the ground, which tripped Du Hui's chariots and horses. As a result, Du Hui was captured by Jin Jun and Wei Ke got all the money.
Therefore, later generations used the word "knot grass rank ring" to express gratitude.