That paramparā should be followed. Evaṁ paramparā-prāptam imaṁ rājarṣayo viduḥ (BG 4.2). If we want to understand really Vedic literature, then we must follow the paramparā system. There are four sampradāyas, paramparā: the Rāmanuja sampradāya, Madhvācārya sampradāya, Viṣṇu Svāmī sampradāya, Nimbārka sampradāya. So we belong to the Madhvācārya sampradāya. Fortunately, all these ācāryas, even Śaṅkarācārya, they appeared from South India. This sampradāya, ācārya-sampradāya, is going on all over India. So every sampradāya has got his commentary on the Brahma-sūtra. Therefore Kṛṣṇa says here, brahma sūtra-padaiś caiva hetumadbhir viniścitaiḥ (BG 13.5). Unless a sampradāya, the four sampradāyas, they do not comment on the Brahma-sūtra, he'll not . . . that sampradāya is not accepted. And if you do not accept the sampradāya . . . sampradāya-vihīnā ye mantrās te niṣphalā matāḥ. If you do not take your initiation mantra from the sampradāya, then it is useless. Now there are so many apasampradāya. They do not come in disciplic succession, but becomes guru, teacher. Therefore everything is topsy-turvied. Nobody has got fixed idea what is God. Everyone has created his own philosophy. The whole thing is now confused.
Therefore Kṛṣṇa specifically mentions Brahma-sūtra. Brahma-sūtra-padaiś caiva hetumadbhir viniścitaiḥ (BG 13.5). The sampradāya must have understanding of the Brahma-sūtra, Vedānta-sūtra. So all the sampradāyas, they have got their commentary on the Vedānta-sūtra and . . . even Śaṅkarācārya. But his commentary is not accepted by the Vaiṣṇava ācāryas because he has tried to derive some meaning, interpretation. But there is no question of interpretation. When the things are clear . . . in the Brahma-sūtra, all the sūtras are very clear, so you don't require any interpretation. You can expand the . . . explain very elaborately. That is another thing. But you cannot go beyond the sutra.