Bhagavad Gita 18.68य इमं परमं गुह्यं मद्भक्तेष्वभिधास्यति।भक्ितं मयि परां कृत्वा मामेवैष्यत्यसंशयः ॥

This supreme secret The teachings of the Gita as taught above in the form of a dialogue between Lord Krishna and Arjuna. Why is it called a supreme secret Because it helps one to attain immortality or freedom from the whell of birth and death.He alone, who has devotion, is qualified to receive the teachings of the Gita.Teach with the faith that he is thus doing service to the Lord, the Supreme Teacher.Doubtless may also mean freedom from doubts.