Shatapatha Brahmana 14.1.3.17

14.1.3.17

sa pravṛṇakti arcirasi śocirasi tapo'sītyeṣa vai gharmo ya eṣa tapati sarvam vā etadeṣa tadetamevaitatprīṇāti tasmādāhārcirasi śocirasi tapo'sīti

He puts it on with, 'Flame thou art, glow thou art, heat thou art;'--for the Gharma is he who shines yonder, and he indeed is all that: it is him he thus gratifies, and therefore he says, 'Flame thou art, glow thou art, heat thou art.'