Tathagata cannot be described

When we feel the urge to reflect on qualities, motives of the Enlightened Being, when we try to envisage what his thought and emotions look like, we always should keep in mind that such a being is transcendent, indescribable and cannot be grasped by us.

At one time Venerable Sabhiya Kaccāna was staying at Nādika in the brick house. Then the wanderer Vacchagotta went up to him, and exchanged greetings with him. When the greetings and polite conversation were over, he sat down to one side, and said to Sabhiya Kaccāna:
“Master Kaccāna, does a Realized One exist after death?”
“Vaccha, this has not been declared by the Buddha.”
“Well then, does a Realized One not exist after death?”
“This too has not been declared by the Buddha.”
“Well then, does a Realized One both exist and not exist after death?”
“This has not been declared by the Buddha.”
“Well then, does a Realized One neither exist nor not exist after death?”
“This too has not been declared by the Buddha.”
“Master Kaccāna, when asked these questions, you say that this has not been declared by the Buddha. What’s the cause, what’s the reason why this has not been declared by the Buddha?”
“In order to describe him as ‘possessing form’ or ‘formless’ or ‘percipient’ or ‘non-percipient’ or ‘neither percipient nor non-percipient’, there must be some cause or reason for doing so. But if that cause and reason were to totally and utterly cease without anything left over, how could you describe him in any such terms?”
“Master Kaccāna, how long has it been since you went forth?”
“Not long, reverend: three years.”
“Well, you’ve learned a lot already, let alone what lies ahead!”
SN 44.11

About Nirvana

There is, monks, an unborn — unbecome — unmade — unfabricated. If there were not that unborn — unbecome — unmade — unfabricated, there would not be the case that emancipation from the born — become — made — fabricated would be discerned. But precisely because there is an unborn — unbecome — unmade — unfabricated, emancipation from the born — become — made — fabricated is discerned.

Unanswered questions

“Mālunkyāputta, if there is the view ‘the world is eternal,’ the holy life cannot be lived; and if there is the view ‘the world is not eternal,’ the holy life cannot be lived. Whether there is the view ‘the world is eternal’ or the view ‘the world is not eternal,’ there is birth, there is ageing, there is death, there are sorrow, lamentation, pain, grief, and despair, the destruction of which I prescribe here and now.

“If there is the view ‘the world is finite,’…‘the world is infinite, ’…‘the soul is the same as the body,’…‘the soul is one thing and the body another,’…‘after death a Tathāgata exists,’…‘after death a Tathāgata does not exist,’ the holy life cannot be lived… If there is the view ‘after death a Tathāgata both exists and does not exist,’ the holy life cannot be lived; and if there is the view ‘after death a Tathāgata neither exists nor does not exist,’ the holy life cannot be lived. Whether there is the view ‘after death a Tathāgata both exists and does not exist’ or the view ‘after death a Tathāgata neither exists nor does not exist,’ there is birth, there is ageing, there is death, there are sorrow, lamentation, pain, grief, and despair, the destruction of which I prescribe here and now.

“Therefore, Mālunkyāputta, remember what I have left undeclared as undeclared, and remember what I have declared as declared. And what have I left undeclared? ‘The world is eternal’—I have left undeclared. ‘The world is not eternal’—I have left undeclared. ‘The world is finite’—I have left undeclared. ‘The world is infinite’—I have left undeclared. ‘The soul is the same as the body’—I have left undeclared. ‘The soul is one thing and the body another’—I have left undeclared. ‘After death a Tathāgata exists’—I have left undeclared. ‘After death a Tathāgata does not exist’—I have left undeclared. ‘After death a Tathāgata both exists and does not exist’—I have left undeclared. ‘After death a Tathāgata neither exists nor does not exist’—I have left undeclared.

“Why have I left that undeclared? Because it is unbeneficial, it does not belong to the fundamentals of the holy life, it does not lead to disenchantment, to dispassion, to cessation, to peace, to direct knowledge, to enlightenment, to Nibbāna. That is why I have left it undeclared.

https://suttacentral.net/mn63/en/bodhi