Śatapatha Brāhmaṇa ("of a hundred paths") 9.3.2.1

9.3.2.1

athāto vasordhārāṃ juhoti | atraiṣa sarvo 'gniḥ saṃskṛtaḥ sa eṣo 'tra vasustasmai devā etāṃ dhārām prāgṛhṇaṃstayainamaprīṇaṃstadyadetasmai vasava etāṃ dhārām prāgṛhṇaṃstasmādenāṃ vasordhāretyācakṣate tathaivāsmā ayametāṃ dhārām pragṛhṇāti tayainam prīṇāti

Thereupon he (the Sacrificer) offers the Vasor dhârâ. That whole Agni has now been completed, and he is here the Vasu (good one): to that Vasu the gods offered this shower (dhârâ), whence it is called 'Vasor dhârâ;' and in like manner this (Sacrificer) offers to him this shower, and gratifies him thereby.