Shatapatha Brahmana 6.7.1.13

6.7.1.13

audumbarī bhavati | ūrgvai rasa udumbara ūrjaivainametadrasena bibhartyatho sarva ete vanaspatayo yadudumbaraḥ sarve vā etaṃ vanaspatayo yantumarhanti sarvairetaṃ vanaspatibhirdevā abibharuḥ sarvairevainametadvanaspatibhirbibharti

It is made of udumbara wood (ficus glomerata), for the Udumbara tree is sustenance (sustaining strength), life-sap: by means of sustenance, life-sap, he thus carries him. Moreover, that Udumbara represents all the trees here (on earth), and all the trees (together) are capable of sustaining that (fire): by means of all the trees the gods bore (or, maintained) it, and by means of all the trees does he now bear it.