SB 2.4.5
rajovaca
samicinam vaco brahman
sarva-jñasya tavanagha
tamo visiryate mahyam
hareh kathayatah katham
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Maharaja Pariksit said: O learned brahmana, you know everything because you are without material contamination. Therefore whatever you have spoken to me appears perfectly right. Your speeches are gradually destroying the darkness of my ignorance, for you are narrating the topics of the Lord.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The practical experience of Maharaja Pariksit is disclosed herein, revealing that transcendental topics of the Lord act like injections when received by the sincere devotee from a person who is perfectly uncontaminated by material tinges. In other words, reception of the messages of Srimad-Bhagavatam from professional men, heard by a karma-kandiya audience, never acts miraculously as stated here. Devotional hearing of the messages of the Lord is not like hearing ordinary topics; therefore the action will be felt by the sincere hearer by experience of the gradual disappearance of ignorance.
yasya deve para bhaktir
yatha deve tatha gurau
tasyaite kathita hy arthah
prakasante mahatmanah
(Svetasvatara Upanisad 6.23)
When a hungry man is given food to eat, he feels satiation of hunger and the pleasure of dining simultaneously. Thus he does not have to ask whether he has actually been fed or not. The crucial test of hearing Srimad-Bhagavatam is that one should get positive enlightenment by such an act.