Bṛhadāraṇyaka Upaniṣad ("Great Forest Teaching") 4.4.2

4.4.2

ekībhavati na paśyatītyāhurekībhavati na jighratītyāhurekībhavati na rasayata ityāhurekībhavati na vadatītyāhurekībhavati na śṛṇotītyāhurekībhavati na manuta ityāhurekībhavati na spṛśatītyāhurekībhavati na vijānātītyāhustasya haitasya hṛdayasyāgraṃ pradyotate tena pradyotenaiṣa ātmā niṣkrāmati cakṣuṣṭo vā mūrdhno vānyebhyo vā śarīradeśebhyastamutkrāmantaṃ prāṇonūtkrāmati prāṇamanūtkrāmantam̐ sarve prāṇā anūtkāmanti sa vijñāno bhavati savijñānamevānvavakrāmati | taṃ vidyākarmaṇī samanvārabhete pūrvaprajñā ca

'"He has become one," they say, "he does not see." "He has become one," they say, "he does not smell." "He has become one," they say, "he does not taste." "He has become one," they say, "he does not speak." "He has become one," they say, "he does not hear." "He has become one," they say, "he does not think." "He has become one," they say, "he does not touch." "He has become one," they say, "he does not know." The point of his heart becomes lighted up, and by that light the Self departs, either through the eye, or through the skull, or through other places of the body. And when he thus departs, life (the chief prâna) departs after him, and when life thus departs, all the other vital spirits (prânas) depart after it. He is conscious, and being conscious he follows and departs.
'Then both his knowledge and his work take hold of him, and his acquaintance with former things.'