To hear means to follow, and through this comes realization.
Unless we hear very strictly with great faith to the order of our Spiritual Master, we will not understand what is the mercy of Krishna and how it is coming upon us.
By hearing from the Guru, we can understand what is the desire of Lord within our heart.
See the Lord not with the eyes, but in fact with the ear. The Akshya Vat tree who was near to Arjuna’s chariot , has become immortal by hearing Bhagavad-Gita, what to speak of us.
Subtle effects the gross. Subtle body has to be changed by listening hari-katha.
Bhagavatam should be heard by dhiras, who have controlled their minds & senses.