Śatapatha Brāhmaṇa ("of a hundred paths") 5.5.1.8

5.5.1.8

sa ya eṣa āgneyo 'ṣṭākapālaḥ pūroḍāśo bhavati | tasya hiraṇyaṃ dakṣiṇāgneyo vā eṣa yajño bhavatyagne reto hiraṇyaṃ tasmāddhiraṇyaṃ dakṣiṇā tadagnīdhe dadātyagnirvā eṣa nidānena yadāgnīdhrastasmāttadagnīdhe dadāti

And what cake on eight potsherds there is for Agni, the priest's fee for that is gold; for that offering is for Agni, and gold is Agni's seed: therefore the fee is gold. He gives it to the Agnîdh; for he, the Âgnîdhra, is really the same as Agni: therefore he gives it to the Agnîdh.