《庄子·内篇·大宗师》
子祀、子舆、子犁、子来四个人在一块摆谈说： 谁能够把无当作头，把生当作脊柱，把死当作尻尾，谁能够通晓生死存亡浑为一体的启发，我们就可以跟他交朋友。 
子祀、子舆、子犁、子来四人相与语曰： 孰能以无为首，以生为脊，以死为尻；孰知死生存亡之一体者，吾与之友矣！ 
Zi Si, Zi Yu, Zi Li, and Zi Lai gathered together and said: "Whoever can make nothingness his head, life his spine, and death his tail, and understand the enlightenment of life and death as one, we can be friends with him." 