ps- for those who don't know, it is from this old story ...
The scholar and head monk Shen-hsiu had written a verse on a corridor wall in response to a request by the aged Patriarch:
Our body is the Bodhi Tree,
And our mind is a bright mirror.
At all times diligently wipe them,
So that they will be free from dust.
What disturbed Hui-neng was the statement that our minds collect dust and need to be continually wiped clean; to him our mind, being part of our [true] nature, is always pure and above delusion. Putting this thought into verse, he asked a visitor to write on the wall:
The Tree of Perfect Wisdom is originally no tree.
Nor has the bright mirror any frame.
Buddha-nature is forever clear and pure.
Where is there any dust?
or another alternative version ...
Bodhi is no tree,
nor is the mind a standing mirror bright.
Since all is originally empty,
where does the dust alight?