Most confidential knowledge - only His devotees can understand

A pure Vedantist, or a bhakti-vedanta, instructs followers exactly according to the instructions of the Lord Himself. The Personality of Godhead, both in the Bhagavad-gita and in all other scriptures, has definitely instructed men to follow the Lord only. The Lord is the creator, maintainer and annihilator of everything. The whole manifested creation is existing by His will, and by His will when the whole show will be finished He will remain in His eternal abode with all His paraphernalia.

Before the creation He was there in the eternal abode, and after the annihilation He will continue to remain. He is not, therefore, one of the created beings. He is transcendental. In the Bhagavad-gita the Lord says that long, long ago, the instruction was imparted to Arjuna, the same was instructed to the sun-god, and in course of time, the same instruction, being wrongly handled and being broken, was again reinstructed to Arjuna because he was His perfect devotee and friend. 

Therefore, the instruction of the Lord can be understood by the devotees only and no one else. The impersonalist, who has no idea of the transcendental form of the Lord, cannot understand this most confidential message of the Lord. The word "most confidential" is significant here because knowledge of devotional service is far, far above knowledge of impersonal Brahman. SB 1.5.30