Verse 5.7.1

पुरुषो वाव गौतमाग्निस्तस्य वागेव समित्प्राणो धूमो जिह्वार्चिश्चक्षुरङ्गाराः श्रोत्रं विस्फुलिङ्गाः ॥ ५.७.१ ॥

puruṣo vāva gautamāgnistasya vāgeva samitprāṇo dhūmo jihvārciścakṣuraṅgārāḥ śrotraṃ visphuliṅgāḥ || 5.7.1 ||

1. O Gautama, man is the [sacrificial] fire; speech is his fuel; prāṇa is the smoke; the tongue is the flame; the eyes are the embers; and the ears are the sparks.

Word-for-word explanation:

Gautama, O Gautama; puruṣaḥ vāva agniḥ, man is the fire; vāk eva tasya samit, speech is his fuel; prāṇaḥ dhūmaḥ, prāṇa is the smoke; jihvā arciḥ, the tongue is the flame; cakṣuḥ aṅgārāḥ, the eyes are the embers; śrotram visphuliṅgāḥ, the ears are the sparks.

Commentary:

Speech is said to be the fuel because it is the source of strength. A person who cannot speak is helpless. Prāṇa is the smoke because the breath comes out of the mouth just as smoke comes out of fire. The tongue is the flame because both are red. The eyes are the embers because both appear to be shining. And the ears are the sparks because both spread out and cover a large area.