Śatapatha Brāhmaṇa ("of a hundred paths") 5.3.5.16

5.3.5.16

sa utpunāti | saviturvaḥ prasava utpunāmyacidreṇa pavitreṇa sūryasya raśmibhiriti so 'sāveva bandhuranibhṛṣṭamasi vāco bandhustapojā ityanādhṛṣṭā stha rakṣobhirityevaitadāha yadāhānibhṛṣṭamasīti vāco bandhuriti yāvadvai prāṇeṣvāpo bhavanti tāvadvācā vadati tasmādāha vāco bandhuriti

He purifies with, 'By the impulse of Savitri I purify you with a flawless purifier, with the rays of the sun.' The significance is the same (as before). 'Not downfallen thou art, the friend of Speech, born of heat,'--unimpaired by the Rakshas he means to say when he says, 'not downfallen;'--'the friend of Speech'--as long as there is water in the vital airs, so long (man) speaks with speech: therefore he says, 'the friend of Speech.'