Shatapatha Brahmana 10.1.1.6

10.1.1.6

te yadā stuvate yadānuśaṃsati athāsminnetaṃ vaṣaṭkṛte juhoti tadenameṣa raso'pyeti na vai mahāvratamidaṃ stutaṃ śeta iti paśyanti no mahadidamukthamityagnimeva paśyantyātmā hyagnistadenamete ubhe raso bhūtvāpīta ṛkca sāma ca tadubhe ṛkṣāme yajurapītaḥ

When those (Udgâtris) chant (the stotra), and when he (the Hotri) recites (the sastra) afterwards, then he (the Adhvaryu) offers that (vital fluid, in the form of Soma) unto him (Agni-Pragâpati) at the Vashat-call; and thus this vital fluid enters him. For, indeed, they do not see it to be the Great Rite that lies there being praised, nor the Great Litany, but it is Agni alone they see; for Agni is the self (body), and thus those two, the Rik and the Sâman, enter him in the form of the vital fluid; and thus they both enter (join) the Yagus.