Kena Upanishad 4.3-2

4.3-2

tasmādvai indraḥ atitarāmiva atiśerata iva anyān devān| sa hyenannediṣṭhaṃ pasparśa yasmāt sa hyenatprathamo vidāñcakāra brahmetyuktārthaṃ vākyam ||

Since even Fire and Air knew from the words of Indra alone, and since Indra heard first from Umā's words that It was Brahman, tasmāt vai indraḥ atitarām iva, therefore Indra did excel (the other deities). Hi saḥ enat nediṣṭham pasparśa, inasmuch as he touched It most proximately, because saḥ hi enat prathamaḥ vidāṁcakāra Brahma iti—this sentence has been already explained.