Śatapatha Brāhmaṇa ("of a hundred paths") 11.2.4.2

11.2.4.2

atho itarathāhuḥ eṣa eva pūrṇamā yaccandramā etasya hyanu pūraṇam paurṇamāsītyācakṣate'thaiṣa eva darśo ya eṣa tapati dadṛśa iva hyeṣaḥ

But they also say inversely, 'The full moon is the same as the moon, for after the filling up of the latter there is the night of full moon;' and the new moon (darsa) is the same as that burning (sun), for the latter appears, as it were.