Brihadaranyaka Upanishad 5.5.4

5.5.4

yo'yaṃ dakṣi-ṇe'kṣanpuruṣastasya bhūriti śira ekam̐ śira ekametadakṣaraṃ bhuva iti bāhū dvau bāhū dve ete akṣare svariti pratiṣṭā dve pratiṣṭhe dve ete akṣare tasyopaniṣadahamiti hanti pāpmānaṃ jahāti ca ya evaṃ veda

Of this being who is in the right eye, the syllable 'Bhur' is the head, for there is one head, and there is this one syllable; the word 'Bhuvar' is the arms, for there are two arms, and there are these two syllables; the word 'Swar' is the legs, for there are two legs, and there are these two syllables. His secret name is 'Aham.' He who knows as above destroys and shuns evil.

5.5.4.p1

iti pañcamādhyāye pañcamaṃ brāhmaṇam