Bṛhadāraṇyaka Upaniṣad ("Great Forest Teaching") 2.2.4

2.2.4

imāveva gotamabharadvājāvayamevagotamo'yaṃ bharadvāja imāveva viśvāmitrajamadagnī ayameva viśvāmitro'yaṃ jamadagnirimāveva vasiṣṭhakaśyapāvayameva vasiṣṭho'yaṃ kaśyapo vāgevātrirvācāhyannamadyate'ttirha vai nāmaitadyadatririti sarvasyāttā bhavati sarvamasyānnaṃ bhavati ya evaṃ veda

These two (the two ears) are the Rishis Gautama and Bharadvâga; the right Gautama, the left Bharadvâga. These two (the eyes) are the Rishis Visvâmitra and Gamadagni; the right Visvâmitra, the left Gamadagni. These two (the nostrils) are the Rishis Vasishtha and Kasyapa; the right Vasishtha, the left Kasyapa. The tongue is Atri, for with the tongue food is eaten, and Atri is meant for Atti, eating. He who knows this, becomes an eater of everything, and everything becomes his food.

2.2.4.p1

iti dvitīyādhyāye dvitīyaṃ brāhmaṇam