Śatapatha Brāhmaṇa ("of a hundred paths") 1.4.2.1

1.4.2.1

etaddha vai devā agniṃ gariṣṭhe 'yuñjan | yaddhotṛtva idaṃ no havyaṃ vaheti tametadgariṣṭhe yuktvopāmadanvīryavānvai tvamasyalaṃ vai tvametasmā asīti vīrye samādadhato yathedamaṣyetarhi jñātīnāṃ yaṃ gariṣṭhe yuñjanti tamupamadanti vīryavānvai tvamasyalaṃ vai tvametasmā asīti vīrye samādadhataḥ sa yadamevāsmindadhāti

Now in former times the gods appointed Agni to the chief (office), namely, that of Hotri; and having appointed him to the chief (office) saying 'do thou carry this our oblation!' they cheered him up, saying, 'Surely, thou art vigorous; surely, thou art equal to this!' thereby endowing him with vigour, even as in our own days, when they appoint any one from among their kinsmen to the chief (office), they cheer him up saying 'surely, thou art vigorous; surely, thou art equal to this!' thereby endowing him with vigour. By what, therefore, he recites after this, he eulogizes him, puts vigour into him.