Verse 4.16.1

एष ह वै यज्ञो योऽयं पवते एष ह यन्निदं सर्वं पुनाति यदेष यन्निदं सर्वं पुनाति तस्मादेष एव यज्ञस्तस्य मनश्च वाक्च वर्तनी ॥ ४.१६.१ ॥

eṣa ha vai yajño yo'yaṃ pavate eṣa ha yannidaṃ sarvaṃ punāti yadeṣa yannidaṃ sarvaṃ punāti tasmādeṣa eva yajñastasya manaśca vākca vartanī || 4.16.1 ||

1. He who blows [i.e., air] is the sacrifice. While moving, he purifies all this. Since he purifies all this while moving, he is the sacrifice. The mind and speech are both his paths.

Word-for-word explanation:

Eṣaḥ ha vai yajñaḥ, he is a sacrifice; yaḥ ayam pavate, this one who blows [i.e., air]; eṣaḥ ha, he; yan, while moving; idam sarvam, all this; punāti, purifies; yat, since; eṣaḥ yan idam sarvam punāti, he purifies all this while moving; tasmāt, therefore; eṣaḥ eva yajñaḥ, he is the sacrifice; manaḥ ca vāk ca, mind and speech; tasya vartanī, are his paths.

Commentary:

Anything that moves can clean or purify things, and this process of cleaning or purifying is a kind of sacrifice. Air is called here a sacrifice because it moves and by moving it purifies.

There are two ways by which the air purifies—by speech and by the mind. By speech we utter mantras, and by the mind we understand them. Speech and the mind both operate by the power derived from air.