The universe contracts, the sun, moon, and stars go black; even if blows of the cane shower like rain, and shouts thunder, this still does not measure up to the business of the transcendent methodology of Zen. Even the Buddhas of past, present, and future can only know for themselves; even the Zen masters through the ages have been unable to bring it up entirely. The entire Buddhist canon cannot explain it thoroughly; even Zennists with clear eyes cannot save themselves completely. When you get to this point, how do you ask for instruction? Even to speak the word Buddha is dragging in the mud soaking wet; even to say the word Zen is a total embarrassment. More-developed people who have studied for a long time do not need to wait for it to be said; as for younger students who are just beginning, they should investigate thoroughly.
From Secrets of the Blue Cliff Record: Zen Comments by Hakuin and Tenkei translated by Thomas Cleary, page 6.