Śatapatha Brāhmaṇa ("of a hundred paths") 9.4.4.4

9.4.4.4

atha dakṣiṇe | imau te pakṣāvajarau patatriṇau yābhyāṃ rakṣāṃsyapahaṃsyagne tābhyām patema sukṛtāmu lokaṃ yatra ṛṣayo jagmuḥ prathamajāḥ purāṇā ityamūnetadṛṣīnāha

Then on the southern (right) one, with (Vâg. S. XVIII, 52), 'By these never-decaying, feathered wings of thine wherewith thou repellest the demons, O Agni, may we fly to the world of the righteous whither the erst-born seers went of old!' he thereby alludes to those Rishis.