As evidence for this, Rūpa Gosvāmī quotes from Śrīmad-Bhāgavatam, Eleventh Canto, Fourteenth Chapter, verse 19. This verse is in connection with Lord Kṛṣṇa's instruction to Uddhava, where He says, "My dear Uddhava, devotional service unto Me is just like a blazing fire which can burn into ashes unlimited fuel supplied to it." The purport is that as the blazing fire can burn any amount of fuel to ashes, so devotional service to the Lord in Kṛṣṇa consciousness can burn up all the fuel of sinful activities. For example, in the Gītā Arjuna thought that fighting was a sinful activity, but Kṛṣṇa engaged him on the battlefield under His order, and so the fighting became devotional service. Therefore, Arjuna was not subjected to any sinful reaction.
Śrīla Rūpa Gosvāmī quotes another verse from the Third Canto of Śrīmad-Bhāgavatam, Thirty-third Chapter, verse 6, in which Devahūti addresses her son, Kapiladeva, and says, "My dear Lord, there are nine different kinds of devotional service, beginning from hearing and chanting.