The Gateless Gate, by Ekai, called Mu-mon, tr. Nyogen Senzaki and Paul Reps [1934], at sacred-texts.com
Kyogen said: "Zen is like a man hanging in a tree by his teeth over a precipice. His hands grasp no branch, his feet rest on no limb, and under the tree another person asks him: 'Why did Bodhidharma come to China from India?'
"If the man in the tree does not answer, he fails; and if he does answer, he falls and loses his life. Now what shall he do?"
Mumon's comment: In such a predicament the most talented eloquence is of no use. If you have memorized all the sutras, you cannot use them. When you can give the right answer, even though your past road was one of death, you open up a new road of life. But if you cannot answer, you should live ages hence and ask the future Buddha, Maitreya.