The influence of a pure devotee is such that if someone comes to associate with him with a little faith, one gets the chance of hearing about the Lord from authoritative scriptures like Bhagavad Gita and Srimad Bhagavatam.
Sri Jiva Goswami specifically explained that Srimad Bhagavatam is the original commentary of Vedantasutra.
Unless one studies Srimad Bhagavatam under the guidance of a bonafide Vaishnava Acharya, he will not be able to understand the real purport of the Brahma-sutra. Srimad Bhagavatam is the original commentary of Vedanta-sutra.
Not only the deity is the Lord, Bhagavatam is also Lord and one Lord is helping us to understand another Lord. Bhagavatam is incarnation of the Lord.
Bhagavatam should be heard by dhiras, who have controlled their minds & senses.
1st and 2nd canto (of Srimad Bhagavatam) are the most important. These are the Foundational Things.