Śatapatha Brāhmaṇa ("of a hundred paths") 4.2.1.33

4.2.1.33

sa prathamāyāṃ vā hotrāyām | iṣṭāyāmuttamāyāṃ vānumantrayate tṛmpantu hotrā madhvo yāḥ sviṣṭā yāḥ suprītāḥ suhutā yatsvāheti hotrāṇāmevaiṣā tṛptirathetya pratyaṅṅupaviśatyayāḍagnīdityagnīddhyatra yajatāmuttamaḥ saṃyajati tasmādāhāyāḍagnīditi

When (the libation of) the first, or last fire-priest has been offered, he addresses them (Vâg. S. VII, 15), 'Let the priests’ offices be satisfied, they that have obtained a good sacrifice of sweet drink; they that are well-pleased, when they have obtained good offering with Svâhâ!' for this is the satisfaction of the priests’ (offices). Thereupon he approaches (to the Hotri's hearth) and sits down with his face to the west, with 'The Agnîdh hath sacrificed!' for on this occasion the Agnîdh sacrifices last of those that sacrifice: hence he says, 'The Agnîdh hath sacrificed.'