The enlightened mind is like a bird in flight that leaves no trace of its path. People will say, “A bird just flew by.” In their mind, there is a trace of the bird’s path. This is attachment. For the enlightened practitioner, that moment is already gone—the bird has left no trace of its flight. Like the bird, from moment to moment the enlightened practitioner’s actions do not leave any trace.
from the book The Method of No-Method: The Chan Practice of Silent Illumination