This was said by the Blessed One, said by the Arahant, as I have heard:
“There are these three |felt experiences::pleasant, neutral or painful sensation, feeling felt on contact through eye, ear, nose, tongue, body, mind; second of the five aggregates [vedanā]|, bhikkhus. What three? Pleasant felt experience, painful felt experience, and neither-painful-nor-pleasant felt experience. Bhikkhus, a pleasant felt experience should be seen as |suffering::discomfort, pain, disease, unpleasantness, stress, discontentment, dissatisfaction [dukkha]|; a painful felt experience should be seen as a |thorn::any sharp pointed object, mental dart, piercing pain [salla]|; a felt experience that is neither-painful-nor-pleasant should be seen as |impermanent::unstable, transient, unreliable [anicca]|. When a bhikkhu sees a pleasant felt experience as |[ultimately] dissatisfying::a source of suffering [dukkha]|, a painful felt experience as a thorn, and a felt experience that is neither-painful-nor-pleasant as impermanent, he is called noble, one with perfect understanding, who has completely cut out |craving::wanting, yearning, longing, attachment, lit. thirst [taṇha]|, |unravelled::untied [vivattayi]| the |fetters::chains, bonds, links, things which bind [saṃyojana]|, and |through full understanding of conceit::through complete comprehension of pride, egotism, superiority, comparing oneself [mānābhisamaya]|, has made an end of suffering.”
The Blessed One spoke on this matter. In this regard, it is said:
“One who sees pleasure as ultimately dissatisfying,
who sees pain as a thorn;
And who sees the peaceful, neither-painful-nor-pleasant felt experience,
as impermanent—
That bhikkhu, through perfect understanding,
is liberated at that very point;
Fully accomplished in |direct knowing::experiential realization [abhiññā]|, |tranquil::peaceful, calm [santa]|,
is a |sage::seer, hermit, monk [munī]| |who has gone beyond the yoke::who has transcended bondage [yogātiga]|.”
This matter too was spoken by the Blessed One, as I have heard.