Mumonkan - Case 49: The Epilogue by Mumon

The words and the actions left by Buddha and the patriarchs in these forty-eight
Koans are as precise as laws and judgements, and therein nothing superfluous is
contained. They turn the student monk's brain upside down and hollow out his
eyeballs. They are here in order that each one of you will immediately grasp
truth and must not try to obtain it vicariously from others. Should there be
anyone who thoroughly appropriates everything, the person would seize the true
meaning of all Forty-eight Koans, as listening to a small portion of them. To
such a person, there is no gate to enlightenment, nor steps to the search. He
may go through the gate with no concern of the gatekeepers, as Gensho said,
  "It is the gateless that is every entrance to realization, and to be
   aimless is the genuine aim of the master."
Haku-un also said,
  "Why can one not go through this very gate, although it is so obvious?"
Such stories are indeed as meaningless as mixing milk with red clay. If you
can pass these Forty-eight Koans through the Gateless Gate you will step on
me, Mumon, under your foot. If you cannot pass through the Gateless Gate, you
will betray yourself. As often said, it is easy to illuminate the realization
that everything is empty, but it is difficult indeed to elucidate the knowledge
of distinctions. If you are able to edify the wisdom of differences, the
universe will be well at peace.