Śatapatha Brāhmaṇa ("of a hundred paths") 10.3.4.5

10.3.4.5

atha ha vai yattaduvāca vetthārkamiti puruṣaṃ haiva taduvāca vetthārkaparṇe iti karṇau haiva taduvāca vetthārkapuṣpe ityakṣiṇī haiva taduvāca vetthārkakośyāviti nāsike haiva taduvāca vetthārkasamudgāvityoṣṭhau haiva taduvāca vetthārkadhānā iti dantānhaiva taduvāca vetthārkāṣṭhīlāmiti jihvāṃ haiva taduvāca vetthārkamūlamityannaṃ haiva taduvāca sa eṣo'gnirarko yatpuruṣaḥ sa yo haitamevamagnimarkam puruṣamupāste'yamahamagnirarko'smīti vidyayā haivāsyaiṣa ātmannagnirarkaścito bhavati

And when he said, 'Knowest thou the Arka?' he thereby meant man;--'Knowest thou the two Arka-leaves?' he thereby meant his ears;--'Knowest thou the two Arka-flowers?' he thereby meant his eyes;--'Knowest thou the pod-leaves of the Arka?' he thereby meant his nostrils;--'Knowest thou the two coops of the Arka?' he thereby meant his lips;--'Knowest thou the Arka-grains?' he thereby meant his teeth;--'Knowest thou the bulge of the Arka?' he thereby meant his tongue;--'Knowest thou the root of the Arka?' he thereby meant his food. Now that Arka, to wit, man, is Agni; and verily, whoso regards Agni as the Arka and the man, in his (altar-) body that Agni, the Arka, will be built up even through the knowledge that 'I here am Agni, the Arka.'