Shatapatha Brahmana 11.5.1.13

11.5.1.13

te hocuḥ na vai sā manuṣyeṣvagneryajñiyā tanūrasti yayeṣṭvāsmākamekaḥ syāditi tasmai ha sthālyāmopyāgnim pradaduraneneṣṭvāsmākameko bhaviṣyasīti taṃ ca ha kumāraṃ cādāyāvavrāja so'raṇya evāgniṃ nidhāya kumāreṇaiva grāmameyāya punaraimītyettirobhūtaṃ yo'gniraśvatthaṃ taṃ yā sthālī śamīṃ tāṃ sa ha punargandharvāneyāya

They said, 'Surely, there is not among men that holy form of fire by sacrificing wherewith one would become one of ourselves.' They put fire into a pan, and gave it to him saying, 'By sacrificing therewith thou shalt become one of ourselves.' He took it (the fire) and his boy, and went on his way home. He then deposited the fire in the forest, and went to the village with the boy alone. [He came back and thought] 'Here I am back;' and lo! it had disappeared: what had been the fire was an Asvattha tree (ficus religiosa), and what had been the pan was a Samî tree (mimosa suma). He then returned to the Gandharvas.