Actually it is not right to say that the Buddha is
re-incarnated, because the Buddha is completely freed from the
cycle of rebirth.
Buddha nature is Unborn. No matter who you are, how evil or good
you are, your Buddha Nature is Perfect and Complete. Because of
this, each of us definitely have the chance to be Awakened, and
WILL be awakened. Buddha Nature is all pervading like space and
eternal, yet sentient beings have forgotten about it for
uncountable aeons in the cycle of rebirth... Therefore the Buddha
appears in his Nirmanakaya form with 32 major marks and 80 minor
marks in order to expound the dharma to sentient beings who are
able to receive them.
Therefore it is not because the Buddha is still under the cycle of
reincarnation but appears in samsara due to his vows/compassion for
sentient beings. The Buddhas will be reincarnated when he observes
that the Cause and Conditions for him to turn the dharma wheel is
ripe. Below are the conditions that Shakyamuni Buddha observed
before deciding his birth:
http://www.saigon.com/~anson/ebud/ebdha165.htm#[01]
Our Bodhisatta (1) was born in Tusita Heaven (2) as a Deva (3)
by the name of Svetaketu. The Devas in Tusita Heaven were happy.
The time had come for the Bodhisatta to be born in the world for
the last time. The Devas invited the Bodhisatta to be born on
earth.
The Bodhisatta looked down at the world to make sure that the five
requirements necessary for His final birth in the world were met.
These five requirements are as follows:
1. The right time - The life span of human beings at a time a
Buddha is born is between 100 and 100,000 years. If the life span
is very short, human beings want to enjoy their short life to the
fullest and tend to be very fond of material things. If the life
span is very long, they tend to forget the impermanence of life. At
this time the Bodhisatta found that the life span was one hundred
and twenty years.
2. The right continent - All Buddhas are born in India (known as
Jumbudipa at the time of the Buddha). This is because the people of
India are spiritually more advanced than people in other countries,
and so are more ready for a Buddha.
3. The right area - The city of Kapilavatthu was chosen as the city
of the future Buddha, as there was a just and good king and many
righteous people living there.
4. The right caste - A Buddha is always born in a high caste -
Either a royal caste or a priestly caste. This is necessary, as
often persons born in a low caste are not accepted by
society.
5. The right mother - The mother of a Buddha has to be very pure.
She is a person who has resolved to be a mother of a Buddha and
observed the five precepts for many countless past lives. The
chosen mother was Queen Mahaa Maayaa, wife of King Suddhodana of
Kapilavatthu.
The Bodhisatta saw that the five requirements were met.
Lastly, I shall paste below a portion of the Avatamsaka Sutra,
this verse is found in the
Daily Buddhist Verses:
Buddha's body is always
apparent,
Filling the entire cosmos,
Always intoning far-reaching sound
Shaking all lands in all quarters.
Buddha manifests bodily everywhere,
Entering into all worlds,
Revealing occult spiritual power
According to the inclinations of beings.
Buddha appears before all beings
In accordance with their minds;
What the sentient beings see
Is the Buddha's mystic power.
His radiance has no bounds
And his teaching too is infinite;
Buddha children enter and observe
According to their knowledge.
The Buddha's body has no birth
Yet can appear to be born.
The nature of reality is like space:
Therein do the Buddhas dwell.
No abiding, yet no departing:
Everywhere the Buddha's seen;
His light reaches everywhere,
His fame is heard afar.
No substance, no abode,
And no origin that can be found;
No signs, no form:
What appears is like reflections.
- Avatamsaka Sutra p. 164-165
