Shatapatha Brahmana 11.1.6.19

11.1.6.19

sa indro'gnīṣomau bhrātarāvabravīt anena vāṃ kāmapreṇa yajñena yājayāni yena māmidam pitā prajāpatirayīyajaditi tatheti tāvayājayattāviṣṭvākāmayetāmāvamevedaṃ sarvaṃ syāveti tayorannāda evānyataro'bhavadannamanyataro'nnāda evāgnirabhavadannaṃ somo'nnādaśca vā idaṃ sarvamannaṃ ca

Indra spake unto his brothers Agni and Soma, 'Let me perform for you this wish-fulfilling sacrifice which our father Pragâpati has just performed for me.'--'So be it!' they said. He accordingly performed it for them. Having sacrificed, those two desired, 'Would that we were everything here!' One of them became the eater of food, and the other became food: Agni became the eater of food, and Soma food; and the eater of food, and food, indeed, are everything here.