yasya deve parā bhaktir yathā deve tathā gurau tasyaite kathitā hy arthā prakāśante mahātmanaḥ

"The real import of the scriptures is revealed to one who has unflinching faith in both the Supreme Personality of Godhead and the spiritual master." Srila Narottama dasa Thakura advises, sadhu-sastra-guru-vakya, hrdaye kariya aikya. The meaning of this instruction is that one must consider the instructions of the sadhu, the revealed scriptures and the spiritual master in order to understand the real purpose of spiritual life. Neither a sadhu (saintly person or Vaisnava) nor a bona fide spiritual master says anything that is beyond the scope of the sanction of the revealed scriptures. Thus the statements of the revealed scriptures correspond to those of the bona fide spiritual master and saintly persons. One must therefore act with reference to these three important sources of understanding.