Śatapatha Brāhmaṇa ("of a hundred paths") 11.2.4.9

11.2.4.9

taddhaike carū nirvapanti paurṇamāsyāṃ sarasvate'māvāsyāyāṃ sarasvatyā etatpratyakṣaṃ darśapūrṇamāsau yajāmaha iti vadantastadu tathā na kuryānmano vai sarasvānvākṣarasvatī sa yadevaitāvāghārāvāghārayati tadevāsya darśapūrṇamāsāviṣṭau bhavatastasmādetau carū na nirvapet

Now, some prepare two messes of rice, one for Sarasvat on the full moon, and one for Sarasvatî on the new moon, saying, 'We thus clearly make offering to the full and new moon.' But let him not do this; for Sarasvat is the Mind, and Sarasvatî is Speech; and thus, in making libations of ghee to these two, offering is made by him to the full and new moon: let him therefore not prepare these two messes of rice.