Śatapatha Brāhmaṇa ("of a hundred paths") 10.3.3.5

10.3.3.5

vetthāgnimiti hovāca kimeva mā vidvānupodasada ityagniṃ vedeti kamagniṃ vettheti ya etatsarvamagnistaṃ vedeti tasminhokta upāvarurohādhīhi bhostamagnimiti

'Thou knowest Agni,' he said; 'knowing what hast thou come to me?'--'Agni I know.'--'What Agni knowest thou?'--'The Agni who is everything here, him I know.'--On (hearing) this said, he stepped down to him and said, 'Teach me that Agni, sir!'