What the buddha-ancestors realize is reality itself, got to the bottom. Reality itself is everything in Sitting. Everything in Sitting means what is as it is -- form as it is, essence as it is, the body as it is, the mind as it is, the world as it is, cloud and rain as it is; walking, standing up, sitting, and lying down, as it is; grief and joy, movement and stillness, as it is; Zen paraphernalia, stick and whisk, as it is; twirling flower and smiling face, as it is; succeeding to the Method of Sitting and imparting the message, as it is; learning in practice and pursuing awakening, as it is; constancy of pine and integrity of bamboo, as it is.
Sakyamuni Buddha says, "Buddha alone, together with buddha, is directly able to get to the bottom of this: Everything in Sitting is reality itself. Everything in sitting means, in other words, form as it is, essence as it is, the physical as it is, energy as it is, doing as it is, causation as it is, connection as it is, fruition as it is, consequence as it is, and ultimate unity of means and end, as it is."
These words of the Thus-Come, "the ultimate unity of means and end," are the teaching spontaneously expressing itself that everything in Sitting is reality. They are the governor spontaneously expressing himself. They are the study of unity.