[I]n Fukanzazengi Zen Master Dogen points out the example of Shakyamuni Buddha who sat upright zazen for six years, although he was wise enough to know the Buddha Dharma at birth. He also mentions Bodhidharma, who sat facing a wall for nine years after coming to China though he had already attained the mind-seal. Dogen stresses that Buddha-ancestors do not practice zazen as a means to an end.
Therefore, as is said in Gakudo Yojinshu, “Realization lies in practice.” Enlightenment is clearly manifested in the Buddha-ancestors’ zazen. In the same vein, in Bendowa Zen Master Dogen wrote, “To suppose that practice and realization are not one is a view of those outside the way. In Buddha Dharma they are inseparable.” He states that when instructing beginners we must teach them not to expect realization outside of practice. Practice is the immediate, original realization. The practice of beginner’s mind is itself the entire original realization. ...
In other schools zazen is a means to gain enlightenment. Like a raft, it is no longer useful when the goal is achieved. Some people boast about their experiences of great enlightenment and kensho. If their zazen practice regresses because of such an experience, that experience is nothing but a delusion that becomes a hindrance to the continuation of practice.
Zen Master Dogen says that the zazen of the Buddha-ancestors is Buddha’s practice. It is a very simple and plain practice of just continuing to sit, letting go of our views. Such zazen embodies the “situation of Buddha’s house” in which the essence (foundation/enlightenment), expounding (explaining the Dharma) and practice are one and the same. Therefore, there is no need to seek the Buddha outside zazen. Zazen is not a practice that produces a Buddha-ancestor but an action causing the Buddha-ancestors to live as Buddha-ancestors. The Buddha-ancestors are beings who have already clarified all kinds of enlightenment and psychological states. They have nothing more to gain, nothing more to realize. When zazen is valued as a practice performed by those Buddha-ancestors, the content of that zazen is called “nothing to attain nothing to enlighten” (Shobogenzo Zuimonki , book 6).
When there is nothing to be gained, nothing to be realized, sitting zazen is “body-mind dropping off (shinjin datsuraku).” Body-mind dropping off is not a wonderful psychological state to be gained as a result of sitting zazen. Rather, zazen itself is nothing but “body-mind dropping off.” It is to escape all kinds of clinging. When we sit zazen, our body-mind naturally drops off and the true Dharma manifests.