Śatapatha Brāhmaṇa ("of a hundred paths") 6.7.1.3

6.7.1.3

yadveva rukbham pratimucya bibharti | asau vā āditya eṣa rukbho no haitamagnim manuṣyo manuṣyarūpeṇa yantumarhatyetenaiva rūpeṇaitadrūpam bibharti

And as to why he puts on and wears the gold plate;--that plate is yonder sun, and man, in his human form, is unable to sustain that fire: it is only in this (solar or divine) form that he bears that (divine) form.