It is clearly stated in the Bhagavad-gītā: bhaktyā mām abhijānāti (BG 18.55). Kṛṣṇa has explained in the Bhagavad-gītā all system—jñāna-yoga system, haṭha-yoga system, -yoga system, rāja-yoga system. But at the end He says that "If anyone actually wants to know Me, that is bhakti." Bhaktyā mām abhijānāti yāvān yaś cāsmi tattvataḥ. If anyone wants to know Kṛṣṇa as He is . . . Kṛṣṇa has different features, especially three: brahmeti paramātmeti bhagavān iti śabdyate (SB 1.2.11)—as impersonal Brahman, all-pervasive Paramātmā, and the Supreme Personality of Godhead. So if anyone wants to know actually what is Kṛṣṇa . . .
Of course, it is not possible to know Kṛṣṇa, but Kṛṣṇa reveals to the devotee, svayam eva sphuraty adaḥ (CC Madhya 17.136), revelation. Just like Kṛṣṇa is explaining Himself in the Bhagavad-gītā. People should know. Why they are searching unnecessarily? Rascaldom. You cannot search out Kṛṣṇa, God, by speculation. If He reveals Himself by His causeless mercy, being merciful upon you, being pleased upon you, then you can understand Kṛṣṇa. You cannot search out Kṛṣṇa. That is not possible.