Srimad-Bhagavatam: Canto 6 - Chapter 1 - Verse 31
Sanskrit:
निगीर्णोऽप्यसुरेन्द्रेण न ममारोदरं गत: ।महापुरुषसन्नद्धो योगमायाबलेन च ॥ ३१ ॥
ITRANS:
nigīrṇo ’py asurendreṇana mamārodaraṁ gataḥmahāpuruṣa-sannaddhoyoga-māyā-balena ca
Translation:
The protective armor of Nārāyaṇa, which Indra possessed, was identical with Nārāyaṇa Himself, the Supreme Personality of Godhead. Protected by that armor and by his own mystic power, King Indra, although swallowed by Vṛtrāsura, did not die within the demon’s belly.