Śatapatha Brāhmaṇa ("of a hundred paths") 3.2.2.16

3.2.2.16

athāsmai vratam prayacati | atinīya mānuṣaṃ kālaṃ sāyaṃdugdhamapararātre prātardugdhamaparāhṇe vyākṛtyā eva daivaṃ caivaitanmānuṣaṃ ca vyākaroti

He (the Adhvaryu) hands the fast-food to him, after letting the ordinary (meal-)time pass,--viz. the evening-milk in the latter part of the night, and the morning-milk in the afternoon,--for the sake of distinction: he thereby distinguishes the divine from the human.