Śatapatha Brāhmaṇa ("of a hundred paths") 6.6.1.3

6.6.1.3

sa yadāgnāvaiṣṇavameva nirvapet | netare haviṣī adhvarasyaiva dīkṣaṇīyaṃ kṛtaṃ syānnāgneratha yaditare eva haviṣī nirvapennāgnāvaiṣṇavamagnereva dīkṣaṇīyaṃ kṛtaṃ syānnādhvarasya

Now were he to prepare only the one for Agni and Vishnu, and not the other two oblations, then only the initiation (offering) of the (Soma) sacrifice would be performed, and not those of Agni (the fire-altar); and were he to prepare only the other two oblations, and not the one to Agni and Vishnu, only the initiation (offering) of Agni would be performed, and not that of the sacrifice.