Śatapatha Brāhmaṇa ("of a hundred paths") 11.2.6.2

11.2.6.2

prāṇa evāsyedhmaḥ prāṇena hīdaṃ sarvamiddhaṃ yatprāṇabhṛnnimiṣadyadejati sa vidyādahamevaiṣa idhma iti

The fuel, indeed, is its breath (of the mouth), for it is by the breath that everything here is kindled (animated) that has breath and moves twinkling with its eyelids: let him know that it is he himself that is that fuel.