The Final Liberating Relinquishment:

When ignorance of the 4 Noble Truths finally
fully evaporates, then:
One no longer clings neither to any sense pleasures, any views,
nor any rules and
rituals!
One no longer clings to any idea of a "self, I, Me, Ego, Soul, or
any Identity" whatsoever...
When one does not cling, then one is not agitated! One thus remains
silently imperturbable...
When
mental perturbation is impossible, one attains the state of Nibbāna right there!
One then understands: Rebirth is ended, this Noble life has been
fully completed,
what had to be done is done, there is no more relapsing into any state of
being...
More on
Nibbāna
A quenched state of Peace, Freedom, and supreme Bliss:
The_2_Nibbanas,
The_Uncreated,
How_to_Enter,
Doctrine of Nibbana,
The_Signless_Nibbana,
Nibbana_Still,
Imperturbable_Equanimity,
Climax of
Calm, Final Freedom,
The
Proximate Cause,
Peace,
What_is_Nibbana,
Nibbana or non-return,
Reaching
Peace,
Nibbana_True_Peace,
The_Entrance,
The_Unborn_State.

Nibbāna is a
Phase Transition of Consciousness!
Source:
Majjhima Nikāya I 68: The shorter speech on the Lion's Roar.