Fukanzazengi IX: Essential Pivot.

Fukanzazengi continues:

In general, [the patriarchs] of this world and of other directions, of the Western
Heavens and of the Eastern Lands, all similarly maintain the Buddha’s posture,
and solely indulge in the custom of our religion. They simply devote themselves
to sitting, and are caught by the still state.

Master Dogen again presents sitting in zazen as the essential standard and custom of Buddhism.

Although there are myriad distinctions and thousands of differences, we
should just practice [za]zen and pursue the truth.

He often recognises the great diversity in the world ('the myriad things') in his writings, but here he presents zen practice as indispensable to the pursuit of the truth within that diversity.

Why should we abandon our own seat on the floor to come and go without purpose through the dusty borders of foreign lands? If we misplace one step we pass over the moment of the present.

The truth is right here/ right now when we realise it in our own practice. We don't need to travel to mystical, foreign places to find it. It's easy to go off on a whim with some lofty goal in mind and miss the truth of the present situation.

We have already received the essential pivot which is the human
body: we must never pass time in vain. We are maintaining and relying upon
the pivotal essence which is the Buddha’s truth: who could wish idly to enjoy
sparks [that fly] from flint? What is more, the body is like a dewdrop on a blade
of grass. Life passes like a flash of lightning. Suddenly it is gone. In an instant
it is lost.

.

Master Dogen sees the impermanent, fragile human body as an 'essential pivot' as we can use our body to realise the truth in zen practice. He combines this image of a 'pivot' with our 'maintaining and relying on the Buddha's truth'. This is the view of Buddhist practice where this very moment is rendered the essential turning point or 'pivot' where we realise our inherent freedom: In zazen we realise that we are generally deluded by perceptions and thoughts ('body and mind'), and that, in a moment of sincere practice, we can allow them to drop off and realise them for what they actually are and allow them to realise us as what we are ('dropping off body and mind'). 'Sparks flying from a flint' suggests things which may be attractive and distracting but which are ultimately fleeting and not substantial (it suggests life where we are distracted by our thoughts and fantasies).

Impermanence is a universal theme in Buddhism; our lives are short when looked at from a broader perspective. Buddhist masters often seek to encourage us to use our time to realise the Great Matter of our life.