According to a common koan (The Book of Serenity, The Blue Cliff Record, and Dogen’s Shinji Shobogenzo), one day the Buddha ascended the platform to address an assembly of followers. As he was settling onto his seat, the Bodhisattva Manjushri struck the gavel and declared, “Clearly observe the Dharma of the King of Dharma; the Dharma of the King of Dharma is thus.” The Buddha then got down from the seat.
Careful study of the actions of these two is instructive. At first it sounds like Manjushri is just announcing the presence of the Buddha, but what he's actually saying is far more interesting. “Clearly observe,” Manjushri said, “the Dharma of the King of Dharma.” But the Buddha-dharma is that teaching that goes beyond what words can express. It's ineffable; it’s not a thing and it’s not an object, so how can it be observed? But in saying “Clearly observe the Dharma of the King of Dharma,” Manjushri, the Bodhisattva of Wisdom, is telling us exactly how it needs to be observed. It is to be observed clearly, without obstruction, with nothing in the way, including our mind’s usual interpretation of what we see.
“The Dharma of the King of Dharma is thus,” Manjushri continues. This was the Buddha’s great realization: suchness, things just as they are. This is precisely what Zen students are working on from the very first moment they begin practicing. We sit down on the zafu to see things as they are and to manifest our self-nature as enlightened nature. As Dogen says in Shobogenzo Inmo (“Suchness”), “To do zazen is to manifest buddha mind, is to manifest suchness.”
According to Dogen, the best practice for realizing suchness, for seeing things as they truly are, is that of shikantaza. Literally, shikantaza means “just sitting.” Anything added to “just sitting,” such as “just sitting to realize enlightenment” or even “just sitting to be like the Buddha” is not true shikantaza; something extra has been added. It is not “just sitting to see things as they are” or “just sitting to manifest our self-nature as enlightened nature.” While these things may, in fact, occur, shikantaza is zazen which is practiced without expectation of any reward, even enlightenment. It is just being yourself, right here, right now.
“Clearly observe the Dharma of the King of Dharma,” Manjushri said. “The Dharma of the King of Dharma is thus.” What more needs to be said beyond that? There was nothing more to say, so the Buddha simply stepped down from the platform in acknowledgement of the completeness of Manjushri’s words (which actually was a form of comment in itself).