Chandogya Upanishad 8.12.4

8.12.4

atha yatraitad ākāśam anuviṣaṇṇaṃ cakṣuḥ sa cākṣuṣaḥ puruṣo darśanāya cakṣuḥ \
atha yo vededaṃ jighrāṇīti sa ātmā gandhāya ghrāṇam \
atha yo vededam abhivyāharāṇīti sa ātmā abhivyāhārāya vāk \
atha yo vededaṃ śṛṇvānīti sa ātmā śravaṇāya śrotram \\812.4\

Now, where the sight merges in Ākāśa (inside the eye, i.e., the black pupil of the eye), (there exists) that which is the person in the eye; and the eye is only for (his) seeing.footnote{} And he who knows 'I smell this', is the Ātman; the nose is for smelling. And he who knows 'I speak this', is the Ātman, the organ of speech is for speaking. And he who knows 'I hear this', is the Ātman; the ear is for hearing.