Śatapatha Brāhmaṇa ("of a hundred paths") 5.3.2.8

5.3.2.8

atha bārhaspatyaṃ carumadhiśrayati | tam maitreṇa pātreṇāpidadhāti tadājyamānayati tattaṇḍulānāvapati sa eṣa ūṣmaṇaiva śrapyate varuṇyo vā eṣa yo 'gninā śṛto 'thaiṣa maitro ya ūṣmaṇā śṛtastasmādūṣmaṇā śṛto bhavati tayorubhayoravadyannāha mitrābṛhaspatibhyāmanubrūhītyāśrāvyāha mitrābṛhaspatī yajeti vaṣaṭkṛte juhoti

He then puts the pap for Brihaspati on (the fire), covers it with the vessel for Mitra's (pap), pours the butter (into the latter), and throws in the (larger) rice-grains. It is cooked merely by the hot steam; for what is cooked by fire belongs to Varuna, and what is cooked by hot steam belongs to Mitra: therefore it is cooked by hot steam. Making cuttings from both these sacrificial dishes, he says, 'Pronounce the invitatory prayer to Mitra and Brihaspati!' Having called for the Sraushat, he says, 'Pronounce the offering-prayer to Mitra and Brihaspati!' and offers as the Vashat is uttered.