sn.45.169 Saṁyutta Nikāya (Linked Discourses)

“Bhikkhus, there are these three feelings. What three? Pleasant feeling, painful feeling, neither-painful-nor-pleasant feeling. These are the three feelings. The Noble Eightfold Path is to be developed for direct knowledge of these three feelings, for the full understanding of them, for their utter destruction, for their abandoning.”