Dragon murmurings in a dried-up tree aren’t used up
-Xuedou
A student asked Xishuang, “What is ‘dragon murmurings in a dried-up tree’?” Xishuang replied, “I still have joy.”
A Student asked Caoshan, “What is ‘dragon murmurings in a dried-up tree’?” Caoshan replied, “The bloodline is not cut off.”
A student asked, "Who can hear this?" Caoshan said, "In the whole world, there is no one who does not hear it." The student asked, "What book is 'dragon murmurings' taken from?" Caoshan said, "I don't know what book it's from, but all who hear it die."
-from Blue Cliff Record, Case 2 (verse and commentary)