The One thus come & thus
gone!

The
Buddha
once explained:
Bhikkhus, this world has
been fully understood by the Tathāgata.
The Tathāgata is completely released from this world.
The origin of this world has been fully understood by the
Tathāgata.
The origin of this world has been completely abandoned by the
Tathāgata.
The ceasing of this world has been fully understood by the
Tathāgata.
The ceasing of this world has been completely realized by the
Tathāgata.
The way leading to the ceasing of this world has been fully understood
by
the Tathāgata and this way has been completely developed by the
Tathāgata.
Bhikkhus, in the world with its devas, maras, and brahmas, with its
recluses
and priests, among humankind with its princes and people, whatever is
seen,
heard, sensed, cognized, attained, sought after, & reflected upon by the
mind,
all that is fully understood by the Tathāgata. It is therefore he is
called the
Tathāgata. Bhikkhus, from the night, when the Tathāgata awakened to this
unsurpassable perfect enlightenment & until the night, when he passes
away
into the Nibbana-element with no trace left, whatever he speaks, says,
and
explains all that is true, correct, just and exactly so, and not
otherwise at all!
It is therefore he is called the Tathāgata. As the
Tathāgata says, so he
does..
As the Tathāgata does, so he says. It is therefore he is called the
Tathāgata.
In the world with its devas, maras, and brahmas, with its recluses and
priests,
among humankind with its princes and people, the Tathāgata is the
conqueror,
the undefeated, the all-seeing, the wielder of power....
It is therefore he is called the Tathāgata!
Itivuttaka
112

Full text here:
https://what-buddha-said.net/library/ati_website/html/tipitaka/kn/iti/index.htmliti.4.106-112x.irel.html#iti-112

Comments:
The designation
Tathāgata has 2 (contracted) meanings:
Tatha + gata = Thus come (to Enlightenment)
Tath + agata = Thus gone (beyond to Nibbana)
More on the
Buddha:
Samma-sambodhi,
SammaSamBuddho!,
The_10_Future_Buddhas,
Metteyya,
Next
Buddha,
How-2-Meet_Buddha_Metteyya?,
Buddha_Contemplation,
Sumedhas_Similes,
Well_Gone,
Master_Presence,
The_Blessed_One,
Life_of_Buddha