The servants of the demigods reached the assembly of Indra, and thus, while all the residents of the three heavens listened, they explained to Indra the supreme power of Nārāyaṇa. When Indra heard of Nara-Nārāyaṇa Ṛṣi and became aware of his offense, he was both frightened and astonished.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
इन्द्रायानम्य सदसि शृण्वतां त्रिदिवौकसाम् । ऊचुर्नारायणबलं शक्रस्तत्रास विस्मितः
indrāyānamya sadasi śṛṇvatāṃ tridivaukasām | ūcurnārāyaṇabalaṃ śakrastatrāsa vismitaḥ
SB 11.4.16