Śrī brahma-saṁhitā 5.59
bhaktim apy uttamāṁ labhet
pramāṇaiḥ — by scriptural evidence; tat — of them; sat-ācāraiḥ — by theistic conduct; tat — of them; abhyāsaiḥ — by practice; nirantaram — constantly; bodhayan — awakening; ātmanā — by one's own intelligence; ātmānam — the self; bhaktim — devotion; api — certainly; uttamām — the highest; labhet — one can attain.
The highest devotion is attained by slow degrees by the method of constant endeavor for self-realization with the help of scriptural evidence, theistic conduct and perseverance in practice.
Evidence—the devotional scriptures, e.g., Śrīmad-Bhāgavatam, the Vedas, the Purāṇas, the Gītā, etc. Theistic conduct—the conduct of pious persons (sādhus) who are pure devotees and the conduct of those pious persons who practice devotion to Godhead actuated by spontaneous love. Practice—to learn about the ten basic principles (daśa-mūla) from the śāstras and on receiving the name of Hari as laid down in the same, embodying the name, form, quality and activity of the Divinity. To practice the chanting of the name by serving Him night and day. By this are meant study of the śāstras and association with the sādhus. The tenfold offense to holy name ceases by serving the name of Hari and simultaneously practicing pious conduct. "Practice" is no other than following the mode of service of the name practiced by the sādhus without offense. By perseverance in such practice and devotion characterized by love which is the fruit of spiritual endeavor makes her appearance in the pure essence of the soul.