Indra was surprised to see that Vrtrasura, undisturbed, was fixed in devotional service to the Lord, for such a mentality is impossible for a demon. However, by the grace of the Supreme Personality of Godhead, anyone can become an exalted devotee

Expressions researched:
"Indra was surprised to see that Vrtrasura, undisturbed, was fixed in devotional service to the Lord, for such a mentality is impossible for a demon. However, by the grace of the Supreme Personality of Godhead, anyone can become an exalted devotee"

SB Canto 6

Indra was surprised to see that Vṛtrāsura, undisturbed, was fixed in devotional service to the Lord, for such a mentality is impossible for a demon. However, by the grace of the Supreme Personality of Godhead, anyone can become an exalted devotee (striyo vaiśyās tathā śūdrās te 'pi yānti parāṁ gatim). An unalloyed devotee is sure to return home, back to Godhead.

SB 6.12.19, Translation and Purport:

Indra said: O great demon, I see by your discrimination and endurance in devotional service, despite your dangerous position, that you are a perfect devotee of the Supreme Personality of Godhead, the Supersoul and friend of everyone.

As stated in Bhagavad-gītā (6.22):

yaṁ labdhvā cāparaṁ lābhaṁ

manyate nādhikaṁ tataḥ

yasmin sthito na duḥkhena

guruṇāpi vicālyate

"Established in Kṛṣṇa consciousness, one never departs from the truth, and upon gaining this he thinks there is no greater gain. Being situated in such a position, one is never shaken, even in the midst of the greatest difficulty." An unalloyed devotee is never disturbed by any kind of trying circumstance. Indra was surprised to see that Vṛtrāsura, undisturbed, was fixed in devotional service to the Lord, for such a mentality is impossible for a demon. However, by the grace of the Supreme Personality of Godhead, anyone can become an exalted devotee (striyo vaiśyās tathā śūdrās te 'pi yānti parāṁ gatim). An unalloyed devotee is sure to return home, back to Godhead.