Fukanzazengi, Dogen Zenji writes:
The Way is basically perfect and all-pervading. How could it be contingent upon practice and realization? The Dharma vehicle is free and untrammeled. What need is there for man’s concentrated effort? Indeed, the whole body is far beyond the world's dust. Who could believe in a means to brush it clean? It is never apart from right where one is. What is the use of going off here and there to practice?
And yet, if there is the slightest discrepancy, the Way is as distant as heaven from earth. If the least like or dislike arises, the Mind is lost in confusion. Suppose one gains pride of understanding and inflates one's own enlightenment, glimpsing the Wisdom that runs through all things, attaining the Way and, clarifying the Mind, raising an aspiration to escalate the very sky. One is making the initial, partial excursions about the frontiers but is still somewhat deficient in the vital Way of total emancipation.
Need I mention the Buddha, who was possessed of inborn knowledge? The influence of his six years of upright sitting is noticeable still. Or Bodhidharma's transmission of the mind-seal? The fame of his nine years of wall-sitting is celebrated to this day. Since this was the case with the saints of old, how can men of today dispense with negotiation of the Way?
You should therefore cease from practice based on intellectual understanding, pursuing words and following after speech, and learn the backward step that turns your light inwardly to illuminate yourself. Body and mind of themselves will drop away, and your original face will be manifest. If you want to attain suchness, you should practice suchness without delay.