Shrimad Bhagavad Gita As It Is -Shri Shrimad A.C Bhaktivedanta Swami Prabhupada
Knowledge of the Absolute
Chapter 7: Verse-1
One should therefore begin yoga practice as directed in the last verse of the Sixth Chapter. Concentration of the mind upon krsna the Supreme is made possible by prescribed devotional service in nine different forms, of which sravanam is the first and most important. The Lord therefore says to Arjuna, tac chrnu, or “Hear from Me.” No one can be a greater authority than Krsna, and therefore by hearing from Him one receives the greatest opportunity to become a perfectly krsna conscious person. One has therefore to learn from Krsna directly or from a pure devotee of Krsna—and not from a nondevotee upstart, puffed up with academic education.In the Srimad-Bhägavatam this process of understanding Krsna, the Supreme Personality of Godhead, the Absolute Truth, is described in the Second Chapter of the First Canto as follows:
“To hear about krsna from Vedic literatures, or to hear from Him directly through the Bhagavad-gita, is itself righteous activity. And for one who hears about Krsna, Lord Krsna, who is dwelling in everyone’s heart, acts as a best-wishing friend and purifies the devotee who constantly engages in hearing of Him. In this way, a devotee naturally develops his dormant transcendental knowledge. As he hears more about krsna from the Bhägavatam and from the devotees, he becomes fixed in the devotional service of the Lord. By development of devotional service one becomes freed from the modes of passion and ignorance, and thus material lusts and avarice are diminished. When these impurities are wiped away, the candidate remains steady in his position of pure goodness, becomes enlivened by devotional service and understands the science of God perfectly. Thus bhakti-yoga severs the hard knot of material affection and enables one to come at once to the stage of asamsayam-samagram, understanding of the Supreme Absolute Truth Personality of Godhead.”  Therefore only by hearing from krsna or from His devotee in krsnaconsciousness can one understand the science of Krsna.
- Bhäg. 1.2.17–21