DN 15:29

'Pleasant feeling is impermanent, conditioned, dependently-arisen, bound to decay, to vanish, to fade away, to cease - and so too are painful feeling and neutral feeling. So anyone who, on experiencing a pleasant feeling, thinks: "This is my self", must, at the cessation of that pleasant feeling, think: "My self has gone!" and the same with painful and neutral feelings. Thus whoever thinks: "Feeling is my self" is contemplating something in this present life that is impermanent, a mixture of happiness and unhappiness, subject to arising and passing away. Therefore it is not fitting to maintain: "Feeling is my self."