Lord can be known only by the sincere mood of eagerness for service

Lord Brahmā is the first living being, who directly learned the Vedic wisdom from the Lord (tene brahma hṛdā ya ādi-kavaye). Therefore, who can be a more learned Vedāntist than Lord Brahmā? He admits that in spite of his perfect knowledge in the Vedas, he was unable to know the glories of the Lord. Since no one can be more than Lord Brahmā, how can a so-called Vedāntist be perfectly cognizant of the Absolute Truth? The so-called Vedāntist, therefore, cannot enter into the existence of the Lord without being trained in the matter of bhakti-vedānta, or Vedānta plus bhakti. Vedānta means self-realization, and bhakti means realization of the Personality of Godhead, to some extent. No one can know the Personality of Godhead in full, but at least to a certain extent one can know the Absolute Truth, the Personality of Godhead, by self-surrender and a devotional attitude, and by nothing else. In the Brahma-saṁhitā also, it is said, vedeṣu durlabham, or simply by study of Vedānta one can hardly find out the existence of the Personality of Godhead, but the Lord is adurlabham ātma-bhaktau, very easily available to His devotee. Śrīla Vyāsadeva, therefore, was not satisfied simply with compiling the Vedānta-sūtras, but over and above this, by the advice of his spiritual master, Nārada, he compiled the Śrīmad-Bhāgavatam in order to understand the real import of Vedānta. Śrīmad-Bhāgavatam therefore, is the absolute medium by which to understand the Absolute Truth.

SB2.6.35 purport