Śatapatha Brāhmaṇa ("of a hundred paths") 1.7.2.18

1.7.2.18

sā yā purastāllakṣaṇā | sānuvākyā syādasau hyanuvākyā tasyā amuṣyā avastāllakṣma candramā nakṣatrāṇi sūryaḥ

Let the invitatory formula be one that has its distinctive indication (in the form of the name of the respective deity) at the beginning (in front): for the invitatory formula is yonder (sky); and that (sky) yonder has the moon, the stars, and the sun for its mark below.