The Scripture on Infinite Light says, "Rivers, lakes, birds, trees, and forests all invoke Buddha, Truth, and Communion."
In a moment of awareness without discrimination, great wisdom appears. This is like pouring water into the ocean, like working a bellows in the wind. Furthermore, how do you discriminate? "Buddha" is a temporary name for what cannot be seen when you look, what cannot be heard when you listen, whose place of origin and passing away cannot be found when you search.
It covers form and sound, pervades sky and earth, penetrates above and below. There is no second view, no second person, no second thought. It is everywhere, in everything, not something external.
This is why the single source of all awareness is called "Buddha." It doesn't change when the body deteriorates; it is always there. But you still cannot use what is always there. Why? Because, as the saying goes, "Although gold dust is precious, when it gets in your eyes, it obstructs vision." Although buddhahood is wonderful, if you are obsessed with it, it becomes a sickness.
An early Zen master said, "It is not mind, not Buddha, not a thing - what is it?" This says it all. It has brought us the diamond sword that cuts through all obsessions.
Another classical Zen master said, "The slightest entangling thought can cause hellish actions; a flash of feeling can chain you indefinitely. Just end ordinary feelings, and there is no special perception of sages to seek - the perception of sages appears where ordinary feelings end."
Xiatang (birth and death unknown) points out that the awareness basic to Zen is inherently non-discursive; it is not reached by suppression of reason, but by a level of attention beyond that of ordinary sense.