Shatapatha Brahmana 14.3.1.6

14.3.1.6

yāte gharmāntarikṣe śugiti yaivāntarikṣe śugyā triṣṭubhyāgnīdhra iti yaiva triṣṭubhyāgnīdhre sā ta āpyāyatāṃ niṣṭyāyatāṃ tasyai te svāheti nātra tirohitamivāsti

'What fire of thine is in the air,'--just the fire which is in the air;--'what is in the Trishtubh and in the Âgnîdhra,' just that which is in the Trishtubh (metre) and Âgnîdhra (fire-shed);--'may that (fire) of thine increase and become firm: to that (fire) of thine, hail!' in this there is nothing hidden, so to speak.