“Ānanda, it’s when a mendicant perceives: ‘This is peaceful; this is sublime—that is, the stilling of all activities, the letting go of all attachments, the ending of craving, fading away, cessation, extinguishment.’
That’s how a mendicant might gain a state of immersion like this. They wouldn’t perceive earth in earth, water in water, fire in fire, or air in air. And they wouldn’t perceive the dimension of infinite space in the dimension of infinite space, the dimension of infinite consciousness in the dimension of infinite consciousness, the dimension of nothingness in the dimension of nothingness, or the dimension of neither perception nor non-perception in the dimension of neither perception nor non-perception. They wouldn’t perceive this world in this world, or the other world in the other world. And they wouldn’t perceive what is seen, heard, thought, known, attained, sought, or explored by the mind. And yet they would still perceive.”
“But at that time what did Reverend Sāriputta perceive?”
“One perception arose in me and another perception ceased: ‘The cessation of continued existence is extinguishment. The cessation of continued existence is extinguishment.’ Suppose there was a burning pile of twigs. One flame would arise and another would cease. In the same way, one perception arose in me and another perception ceased: ‘The cessation of continued existence is extinguishment. The cessation of continued existence is extinguishment.’ At that time I perceived that the cessation of continued existence is extinguishment.”
There’s different opinions from different venerables on what this samādhi above is referring to.
Venerable Sunyo thinks it’s accessible to stream winners as seeing Nibbāna. In classical Theravada terminology then it’s fruition attainments.
Bhante Aggacitta thinks it’s the touching of Nibbāna with the body only accessible to arahants.
As highlighted here SuttaCentral
“I have truly seen clearly with right wisdom that the cessation of continued existence is extinguishment. Yet I am not a perfected one. Suppose there was a well on a desert road that had neither rope nor bucket. Then along comes a person struggling in the oppressive heat, weary, thirsty, and parched. They’d know that there was water, but they couldn’t physically touch it.
In the same way, I have truly seen clearly with right wisdom that the cessation of continued existence is extinguishment. Yet I am not a perfected one.”
Trainees are only able to see Nibbāna, but not touch nibbāna with the body (personally experience), but the arahants can touch with the body.
So which is it for this perception of Nibbāna? I commonly just map it to arahant fruition attainment as a safe bet.