SB 7.5.4
ekadasura-rat putram
ankam aropya pandava
papraccha kathyatam vatsa
manyate sadhu yad bhavan
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
My dear King Yudhisthira, once upon a time the King of the demons, Hiranyakasipu, took his son Prahlada on his lap and very affectionately inquired: My dear son, please let me know what you think is the best of all the subjects you have studied from your teachers.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Hiranyakasipu did not ask his young son anything that would be very difficult for him to answer; instead, he gave the boy a chance to speak plainly about whatever he thought might be best. Prahlada Maharaja, of course, being a perfect devotee, knew everything and could say what the best part of life is. In the Vedas it is said, yasmin vijñate sarvam evam vijñatam bhavati: if one properly understands God, he can understand any subject matter very nicely. Sometimes we have to challenge big scientists and philosophers, but by the grace of Krsna we emerge successful. It is impossible, practically speaking, for ordinary men to challenge scientists or philosophers concerning genuine knowledge, but a devotee can challenge them because the best of everything is known to a devotee by the grace of Krsna. As confirmed in Bhagavad-gita (10.11):
tesam evanukampartham
aham ajñana-jam tamah
nasayamy atma-bhava-stho
jñana-dipena bhasvata
Krsna, who is situated in the core of everyone’s heart as the Supersoul, dissipates all the ignorance from the heart of a devotee. As a special favor, He enlightens the devotee with all knowledge by putting before him the torch of light. Prahlada Maharaja, therefore, knew the best of knowledge, and when his father inquired from him, Prahlada gave him that knowledge. Prahlada Maharaja was able to solve the most difficult parts of problems because of his advanced Krsna consciousness. Therefore he replied as follows.