Garudapurana 1.126.2

1.126.2

sāmānyamaṇḍalaṃ nyasya dhātāraṃ dvāradeśataḥ /
vidhātāraṃ tathā gaṅgāṃ yamunāṃ ca mahānadīm //

Having arranged the common maṇḍala, [one should worship] Dhātṛ at the entrance, / as well as Vidhātṛ, and the Gaṅgā and Yamunā, the great rivers;