Bṛhadāraṇyaka Upaniṣad ("Great Forest Teaching") 3.7.23

3.7.23

yo retasi tiṣṭhanretaso'ntaro yam̐ reto na veda yasya retaḥ śarīraṃ yo reto'ntaro yamayatyeṣa ta ātmāntaryāmyamṛto'dṛṣṭo draṣṭāśrutaḥ śrotāmato mantāvijñāto vijñātā nānyo'to'sti draṣṭā nānyo'to'stiśrotā nānyo'to'sti mantā nānyo'to'sti vijñātaiṣa ta ātmāntaryāmyamṛto'to'nyadārtaṃ tato hoddālaka āruṇirupararāma

'He who dwells in the seed, and within the seed, whom the seed does not know, whose body the seed is, and who pulls (rules) the seed within, he is thy Self, the puller (ruler) within, the immortal; unseen, but seeing; unheard, but hearing; unperceived, but perceiving; unknown, but knowing. There is no other seer but he, there is no other hearer but he, there is no other perceiver but he, there is no other knower but he. This is thy Self, the ruler within, the immortal. Everything else is of evil.' After that Uddâlaka Âruni held his peace.

3.7.23.p1

iti tṛtīyādhyāye saptamaṃ brāhmaṇam