Bhagvatam Lord Krshna says Himself in Bhagavad-gitä (7.28)"Persons who have acted piously in previous lives and in this life, whose sinful actions are completely eradicated and who are freed from the duality of delusion, engage themselves in My service with determination”
TRANSLATION
King Parikshit inquired from Sukadeva Gosvämi: O learned brähmana, demons are generally sinful, being obsessed with the modes of passion and ignorance. How, then, could Vrträsura have attained such exalted love for the Supreme Personality of Godhead, Näräyana?
PURPORT
In this material world, everyone is obsessed with the modes of passion and ignorance.
However, unless one conquers these modes and comes to the platform of goodness, there is no chance of one's becoming a pure devotee.
This is confirmed by Lord Krshna Himself in Bhagavad-gitä (7.28):
"Persons who have acted piously in previous lives and in this life, whose sinful actions are completely eradicated and who are freed from the duality of delusion, engage themselves in My service with determination.”
Since Vrträsura was among the demons, Mahäräja Parikshit wondered how it was possible for him to have become such an exalted devotee.
Demigods situated in the mode of goodness and great saints cleansed of the dirt of material enjoyment hardly ever render pure devotional service at the lotus feet of Mukunda.
[Therefore how could Vrträsura have become such a great devotee?]
In this material world there are as many living entities as atoms.
Among these living entities, a very few are human beings, and among them, few are interested in following religious principles.