This teaching is from the section The Planes of Realization from “In the Buddha’s Words” by Bhikkhu Bodhi.
The Buddha explains how one becomes the perfected one, an arahant, and shares verses on their qualities.
At Sāvatthi.
"Form, bhikkhus, is impermanent. What is impermanent is suffering; what is suffering is not-self; what is not-self should be seen as, ‘This is not mine, I am not this, this is not my self,’ — thus it should be seen with right wisdom as it really is.
Feeling, bhikkhus, is impermanent. What is impermanent is suffering; what is suffering is not-self; what is not-self should be seen as, ‘This is not mine, I am not this, this is not my self,’ — thus it should be seen with right wisdom as it really is.
Perception, bhikkhus, is impermanent. What is impermanent is suffering; what is suffering is not-self; what is not-self should be seen as, ‘This is not mine, I am not this, this is not my self,’ — thus it should be seen with right wisdom as it really is.
Volitional formations, bhikkhus, are impermanent. What is impermanent is suffering; what is suffering is not-self; what is not-self should be seen as, ‘This is not mine, I am not this, this is not my self,’ — thus it should be seen with right wisdom as it really is.
Consciousness, bhikkhus, is impermanent. What is impermanent is suffering; what is suffering is not-self; what is not-self should be seen as, ‘This is not mine, I am not this, this is not my self,’ — thus it should be seen with right wisdom as it really is.
Seeing thus, bhikkhus, the learned noble disciple becomes disenchanted with form, disenchanted with feeling, disenchanted with perception, disenchanted with volitional formations, and disenchanted with consciousness. Becoming disenchanted, they become dispassionate; through dispassion, they are liberated. When liberated, there is the insight that ‘I am liberated.’"
He knows: ‘Re-birth is ended, the spiritual life has been lived, what had to be done has been done, there is no more coming to any state of being.’ Bhikkhus, in all the realms of beings, in all the worlds, these are highest, these are the foremost, namely, the arahants."
The Blessed One said this. Having spoken, the Well-Gone One, the Teacher, further spoke these words:
"Truly at ease are the arahants, for craving is no longer found in them; The conceit of ‘I am’ is cut off, and the net of delusion is torn apart.
Having arrived at the unperturbed, their minds are serene; In the world, they’re untainted, they have become noble, free from defilements.
Having fully understood the five aggregates, they dwell in the true nature of things; Praiseworthy are these noble beings, true-born children of the Buddha.
Endowed with the seven elements of awakening, Well-trained in the three trainings; These great heroes wander freely, Having abandoned the causes of fear and dread.
Endowed with the ten factors, these great beings are deeply composed; Indeed, they are the foremost in the world, for craving is no longer found in them.
The wisdom of the non-learner has arisen, this is the final accumulation; It is the heartwood of the spiritual life, in which there is no further dependence.
They do not waver in any way, fully liberated from renewed existence; They have attained the state of self-control, these are the conquerors in the world.
Above, across, and below, no attachment is found in them; They roar the lion’s roar, the Buddhas, unsurpassed in the world."
While it not possible to conceptually know the experience of one abiding in Nibbāna (enlightenment), it is helpful to clear any misperceptions that one may have about it and the qualities of an Arahant (an enlightened being).
One typically starts out with doubt about enlightenment and the possibility of attaining it for oneself, and if this is where you are, that’s okay. You can harness this doubt to create an inquisitive mind - to learn, reflect and apply the teachings in practice and then see if the beneficial qualities of mind are arising and growing, and if your relationships are improving. You would like both to be improving and then, it’s only a matter of continued practice till it becomes easy, automatic and second nature that this doubt dissolves to never arise again.
Related Teachings:
The Buddha and the Arahant (SN 22.58) - The Buddha shares the similarities and differences between him and another liberated by wisdom.
The trainee and the Arahant (SN 48.53) - Trainee here is a reference to someone who is a stream-enterer but not an Arahant. The Buddha is sharing this teaching to help an individual see where they’re on the path.
Nine things an Arahant is incapable of doing (AN 9.7) - The Buddha explains to Sutavā, the wanderer, that an arahant is incapable of transgressing in nine ways.
33 Synonyms for Nibbāna (from SN 43.12 - 43.44) - This compilation of similar teachings is an invitation to broaden one’s personal understanding of what the state of Nibbāna is.