nigirno ’py asurendrena
na mamarodaram gatah
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The protective armor of Narayana, which Indra possessed, was identical with Narayana Himself, the Supreme Personality of Godhead. Protected by that armor and by his own mystic power, King Indra, although swallowed by Vrtrasura, did not die within the demon’s belly.