vrtras tu sa katham papah
ittham drdha-matih krsna
asit sangrama ulbane
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Vrtrasura was situated in the blazing fire of battle and was an infamous, sinful demon, always engaged in giving troubles and anxieties to others. How could such a demon become so greatly Krsna conscious?
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
It has been described that a narayana-parayana, a pure devotee, is rarely found even among millions and millions of persons. Therefore Pariksit Maharaja was surprised that Vrtrasura, whose purpose was to give trouble and anxiety to others, was one of these devotees, even on a battlefield. What was the reason for Vrtrasura’s advancement?