Srimad Bhagavatam

References to text SB 5.18.12
SB 5.18.12: All the demigods and their exalted qualities, such as religion, knowledge and renunciation, become manifest in the body of one who has developed unalloyed devotion for the Supreme Personality of Godhead, Vāsudeva. On the other hand, a person devoid of devotional service and engaged in material activities has no good qualities. Even if he is adept at the practice of mystic yoga or the honest endeavor of maintaining his family and relatives, he must be driven by his own mental speculations and must engage in the service of the Lord’s external energy. How can there be any good qualities in such a man?

Text №
There are six principles favorable to the execution of pure devotional service: (1) being enthusiastic, (2) endeavoring with condence, (3) being patient, (4) acting according to regulative principles [such as śravaṇaᚁ kÄŤrtanaᚁ viṣṇoḼ smaraṇam – hearing, chanting and remembering Kṛṣṇa], (5) abandoning the association of nondevotees, and (6) following in the footsteps of the previous ācāryas. These six principles undoubtedly assure the complete success of pure devotional service.
Nectar of Instruction
NoI 3