Digha Nikaya 2:325
SUJATOSukhassa ca pahānā dukkhassa ca pahānā pubbeva somanassadomanassānaṁ atthaṅgamā adukkhamasukhaṁ upekkhāsatipārisuddhiṁ catutthaṁ jhānaṁ upasampajja viharati.
With the giving up of pleasure and pain and the disappearance of former happiness and sadness, they enter and remain in the fourth absorption, without pleasure or pain, with pure equanimity and mindfulness.