Śatapatha Brāhmaṇa ("of a hundred paths") 11.5.1.17

11.5.1.17

sa āśvatthīmevottarāraṇiṃ cakre āśvatthīmadharāraṇiṃ sa yastato'gnirjajñe sa eva sa āsa teneṣṭvā gandharvāṇāmeka āsa tasmādāśvatthīmevottarāraṇiṃ kurvītāśvatthīmadharāraṇiṃ sa yastato'gnirjāyate sa eva sa bhavati teneṣṭvā gandharvāṇāmeko bhavati

He then made himself an upper arani of Asvattha wood, and a lower arani of Asvattha wood; and the fire which resulted therefrom was that very fire: by offering therewith he became one of the Gandharvas. Let him therefore make himself an upper and a lower arani of Asvattha wood, and the fire which results therefrom will be that very fire: by offering therewith he becomes one of the Gandharvas.