So yogis are in the second stage of self-realization, but ultimate realization is Bhagavān. Kṛṣṇas tu bhagavān svayam (SB 1.3.28). Bhagavān has got many expansions, Rāma, Nṛsiṁha, Varāha... First expansion is Balarāma, then Saṅkarṣaṇa, Pradyumna, Aniruddha, then Nārāyaṇa. In this way, Mahā-Viṣṇu, Garbhodakaśāyī Viṣṇu, Kṣīrodakaśāyī Viṣṇu.
In this way the Viṣṇu-tattva is expanded. Advaitam acyutam anādim ananta-rūpam ādyaṁ purāṇa-puruṣaṁ nava-yauvanaṁ ca (Bs. 5.33). So in this way there are many śāstras, many Vedic literature, many explanations. But here Kṛṣṇa gives a special reference to the Brahma-sūtra, Vedānta-sūtra. Jñāna-vairāgya-yuktayā (SB 1.2.12) means one has to learn very nicely Vedānta-sūtra. And the explanation of Vedānta-sūtra, natural comment on Vedānta-sūtra, is Śrīmad-Bhāgavatam. Bhāṣyāyāṁ brahma-sūtrāṇām. Śrīmad-Bhāgavatam is the natural commentary.