Chandogya Upanishad 7.11.2

7.11.2

sa yas tejo brahmety upāste \
tejasvī vai sa tejasvato lokān bhāsvato 'pahatatamaskān abhisidhyati \
yāvat tejaso gataṃ tatrāsya yathākāmacāro bhavati yas tejo brahmety upāste \
asti bhagavas tejaso bhūya iti \
tejaso vāva bhūyo 'stīti \
tan me bhagavān bravītv iti \\711.2\

2. He who reverences Heat as Brahma—he, verily, being glowing, attains glowing, shining worlds freed from darkness. As far as Heat goes, so far he has unlimited Freedom, he who reverences Heat as Brahma.’

‘Is there, Sir, more than Heat?’

‘There is, assuredly, more than Heat.’

‘Do you, Sir, tell me it.’