Srimad-Bhagavatam: Canto 6 - Chapter 1 - Verse 18

Sanskrit:

श्रीशुक उवाचइन्द्रो वृत्रवच: श्रुत्वा गतालीकमपूजयत् ।गृहीतवज्र: प्रहसंस्तमाह गतविस्मय: ॥ १८ ॥

ITRANS:

śrī-śuka uvācaindro vṛtra-vacaḥ śrutvāgatālīkam apūjayatgṛhīta-vajraḥ prahasaṁstam āha gata-vismayaḥ

Translation:

Śukadeva Gosvāmī said: Hearing the straightforward, instructive words of Vṛtrāsura, King Indra praised him and again took the thunderbolt in his hand. Without bewilderment or duplicity, he then smiled and spoke to Vṛtrāsura as follows.

Purport:

King Indra, the greatest of the demigods, was astonished to hear the instructions of Vṛtrāsura, who was supposed to be a demon. He was struck with wonder that a demon could speak so intelligently. Then he remembered great devotees like Prahlāda Mahārāja and Bali Mahārāja, who had been born in the families of demons, and thus he came to his senses. Even so-called demons sometimes have exalted devotion for the Supreme Personality of Godhead. Therefore Indra smiled reassuringly at Vṛtrāsura.