http://www.jenchen.org.sg/vol9no3a.htm
All Form is Non-form
by Venerable Master Shen-Kai
The myriad of things and
phenomena in this world are formed by aggregations of numerous
causes and conditions comprising four elements: earth, water, fire
and wind. As such, they do not have independent natures of their
own. A tree, for example, is the result of a combination of
nutrients, water, sunlight and air. Thus, they are in fact empty
because when the conditions that created and sustained them are no
longer present, these objects will return to emptiness. However, we
don't see them in this light. We think they are real, absolute and
permanent. But they are not. They are dependent upon other
conditions. We need to truly comprehend and awaken to this
fundamental truth of emptiness.
The phrase 'all form is non-form' is from the Diamond Sutra.
Buddha said, "Subhuti, what do you think? Can we use our ordinary
flesh-eyes to see the Tathagatas physical form and thus believe we
are seeing the true Tathagata ?"
Subhuti replied, "No, World-honoured One. We cannot look upon the
unreal form of the Tathagatas manifestation and think we have
perceived the non-arising and non-ceasing true body of the
Tathagata."
How is that? The 16-foot physique of the Tathagata is a bodily form
produced by an aggregation of causes and conditions. When life
ends, that body decays and eventually vanishes. It is not the truly
pure Dharma-kaya of the Tathagata because the Dharma-kaya has no
form to be seen; it is empty and tranquil. How could flesh-eyes of
sentient beings see the true form of the Tathagatas
Dharma-kaya?
Buddha told Subhuti, "Not only is the Tathagatas bodily form a
false form produced by the aggregation of causes and conditions,
which does not have real substance, so is any kind of thing in the
universe, in this world as well as beyond this world. All living
and non-living things, shapes and colours are merely formed by
aggregations of causes and conditions. They are impermanent and
will change as causes and conditions disperse. They are as illusory
as the flower in the mirror or the moon in the water!
"If looking at appearances of objects, sentient beings are able to
lucidly awaken to its aggregation of causes and conditions, and
understand impermanence, their arising and ceasing; and if at that
very instant, distinguishing does not arise, then without
discrimination, they can enter into deep stillness. In stillness,
pure wisdom reveals itself. With supreme wisdom, they realise that
all worldly form is created by causes and conditions. Its nature is
empty; it is not reality. In this way, they will directly perceive
the Tathagatas Dharma-kaya."

Subhuti was the Arahat who best understood emptiness. Thus, with
regards to emptiness, he had profound realisation. We see this in a
story:
Once, Buddha went to the heavenly palace of Trayastrimsas to preach
Dharma to his mother. He only returned to earth after having been
gone for a few months. All of his disciples missed him. When he
returned, they rushed to welcome him, each hoping to be the first
to pay their respects to him. Being the most advanced in
supernatural ability amongst the Buddha's female disciples,
Bhiksuni Lian-hua-se used her supernatural powers and transformed
herself into the image of Saint-king Cakravarti. Then, with great
poise, she went to stand right up in front. She very happily paid
her respects toBuddha and said, "Disciple Lian-hua-se is the first
to pay respects to Buddha today. Oh, Im overjoyed!"
Buddha replied with a smile, "Lian-hua-se, the first to see the
Tathagata wasnt you. It was Subhuti!"
Bhiksuni Lian-hua-se was astonished! Subhuti had not joined in the
queue to welcome the Buddha. How could he have been the first to
meet the Buddha?
Buddha then said, "The bodily form of the Tathagata is not seen by
our perceptions. He who sees the Dharma, sees the Tathagata."

As it turned out, when Buddha returned to earth, Subhuti had been
in the meditation hall sitting in stillness, deeply observing the
emptiness of all things and phenomena, clearly understanding the
reality of inherent emptiness, and thus realising the formless
Dharma-kaya of Tathagata. Even though he had not been there in the
queue, he had in fact truly seen the Tathagata.
Buddha has three bodies (Trikaya). One is 'Nirmana-kaya'(Hua
Sheng), or the 'Emanation Body'. According to the sentient beings'
capacity for understanding, Buddha manifests the illusory forms of
physical bodies in numerous worlds. Because of their heavy karmic
hindrances, some disciples were only able to see the 16-foot golden
body of the Buddha, but were unable to see the 32 physical
characteristics and 80 accompanying physical features of a great
person (i.e. Dvatrimsadvara-laksana and Anuvyanjana).
Another body of Buddha is 'Sambhoga-kaya' (Bao Sheng), or the
'benefiting body', of which are two kinds: one is the 'body which
benefits oneself', and the other is the 'body which benefits
others'. The former is the Buddha's own attainment and awakening to
his meritorious intrinsic pure Buddha-nature, in the state of
Dharma joy. The latter is the appearance of enlightened, liberated
Bodhisattvas to guide beginner-Bodhisattvas (i.e. sentient beings
who emulate Bodhisattvas and practise the Bodhisattva Way)
according to prevailing causalities, enabling these
beginner-Bodhisattvas to benefit from the teachings of Greater
Vehicle (Mahayana) with Dharma joy. Both Nirmana-kaya and
Sambhoga-kaya are physical forms which are visible. However, the
perfect Sambhoga-kaya of Great Bodhisattvas is a form that is
infinite and of awesome majesty. It is not something that ordinary
sentient beings like us can see. What ordinary people see is the
Nirmana-kaya form.
The third body of Buddha, named 'Dharma-kaya'(Fa Sheng), is the
Truth Body of the Tathagata, and also the reality of all phenomena.
It permeates all of space and is omnipresent. An ancient sage said,
"Green bamboos are entirely Dharma-kaya, luxuriant chrysanthemums
are all Prajna; each grass, each tree, all in the ocean of
Buddha-nature. Green bamboos are used for expressing the state of
Dharma-kaya, but bamboos are by no means Dharma-kaya. Luxuriant
chrysanthemums are used for displaying the function of Prajna, but
chrysanthemums are by no means Prajna."
The myriad of things and phenomena in this world are formed by
aggregations of numerous causes and conditions comprising four
elements and five skandhas , arising by causality and ceasing by
causality; their nature is inherently empty. And everything in the
world is as such. They do not exist as individual entities. Hence,
the nature of all things and phenomena is empty, tranquil and all
pervasive. However, people are unaware of this and are grasping on
to their belief that the numerous forms in the universe truly
exist. But if you can truly comprehend this and awaken to the
realisation that the nature of all forms is emptiness, then
instantaneously you perceive the pure Dharma-kaya of Tathagata.