Dazhu Huihai
Japanese:  Daishu Ekai
Great Pearl    Wisdom Ocean
Chinese simplified:  大珠慧海
born:  c. 730
died:  c. 800

place:  China
Chan master:  Mazu (J. Baso)
Chan disciples:  none recorded
surname:  Zhu
This "Huihai" is sometimes confused with another
Zen master,  "Huaihai" (see
Baizhang Huaihai),
both having the same master Mazu, and their
dharma names meaning almost the same thing,
and also sounding almost the same. See
this
page for a more thorough explanation on this
subject.
John Blofeld wrote one of the earliest
translations of Chinese Chan on the stories of
this Zen master:
The Teachings of Hui Hai. c.
1960., included in Osho's
Books I Have Loved.
stories:

Osho
Hyakujo: The Everest of Zen, ch. 1, ch. 2, ch. 4
          oshobob  The Living Workshop                                        
                                                     Zen Masters
When Hui-hai  returned to Yueh Chou, he lived
a retired life, concealing his abilities and
outwardly appearing somewhat mad. It was at
this time that he composed his shastra, called,
"A Treatise Setting Forth the Essential Gateway
to Truth by Means of Instantaneous Awakening."

Later, this book was stolen and brought to the
Yangtze region and shown to Ma Tzu. After
reading it carefully, Ma Tzu declared to his
disciples: "In Yueh Chou there is now a great
pearl. Its luster penetrates everywhere freely
and without obstruction."

Ma Tzu was making a pun on Hui-hai's original
surname of Chu.
..


Now, this is something to be understood and it is
one of the most debated subject matters for
centuries: if enlightenment is sudden, that
means there is no cause to it. It can be sudden
only if it has no causality. If it has any cause,
first the cause has to be produced, then
enlightenment will follow.

Science believes in causality. You provide all the
necessary causes, and this will be the inevitable
outcome. But Zen, in the sense of sudden
enlightenment, drops the idea of causality.
There is no cause that leads to enlightenment...

                                            --Osho
Hyakujo: The Everest of Zen, with Basho's
haikus, ch.2