Śatapatha Brāhmaṇa ("of a hundred paths") 2.3.2.2

2.3.2.2

tadvā eṣa evendraḥ | yadāhavanīyo 'thaiṣa eva gārhapatyo yamo rājāthaiṣa eva naḍo naiṣidho yadanvāhāryapacanastadyadetamaharahardakṣiṇata āharanti tasmādāhuraharaharvai naḍo naiṣidho yamaṃ rājānaṃ dakṣiṇata upanayatīti

Now Indra, in truth, is the same as the Âhavanîya; and king Yama is the same as the Gârhapatya; and Nada Naishadha is the same as the Anvâhâryapakana (Dakshina fire); and because day by day they take that (fire) to the south, therefore indeed they say that day by day Nada Naishadha carries king Yama (further) south.