Wei Wuzi, a high minister of the state of Jin, ordered his son Wei Ke: after his death, the concubine who had not borne a son should be allowed to remarry, rather than be buried alive with him as was the custom.
When his illness worsened, he changed his order, insisting that the concubine be buried with him upon his death.
After his father's death, Wei Ke allowed the concubine to remarry. He explained, "When people are gravely ill, their minds are not clear. I followed the instructions my father gave when he was still of sound mind."
Later, during a battle, an old man knotted grass on the battlefield, tripping Du Hui, a Qin general who was pursuing Wei Ke. That night, Wei Ke dreamed of the old man, who said, "I am the father of the concubine you saved by letting her remarry. I knotted the grass to trip Du Hui to reciprocate your kindness in saving my daughter's life."