SB 7.4.44

śrī-yudhiṣṭhira uvāca
devarṣa etad icchāmo
 vedituṁ tava suvrata
yad ātmajāya śuddhāya
 pitādāt sādhave hy agham
Word for word: 
śrī-yudhiṣṭhiraḥ uvāca — Mahārāja Yudhiṣṭhira inquired; deva-ṛṣe — O best saintly person among the demigods; etat — this; icchāmaḥ — we wish; veditum — to know; tava — from you; su-vrata — having the determination for spiritual advancement; yat — because; ātma-jāya — unto his own son; śuddhāya — who was pure and exalted; pitā — the father, Hiraṇyakaśipu; adāt — gave; sādhave — a great saint; hi — indeed; agham — trouble.
Translation: 
Mahārāja Yudhiṣṭhira said: O best of the saints among the demigods, O best of spiritual leaders, how did Hiraṇyakaśipu give so much trouble to Prahlāda Mahārāja, the pure and exalted saint, although Prahlāda was his own son? I wish to know about this subject from you.
Purport: 

To know about the Supreme Personality of Godhead and the characteristics of His pure devotee, one must inquire from authorities like Devarṣi Nārada. One cannot inquire about transcendental subject matters from a layman. As stated in Śrīmad-Bhāgavatam (3.25.25), satāṁ prasaṅgān mama vīrya-saṁvido bhavanti hṛt-karṇa-rasāyanāḥ kathāḥ: only by association with devotees can one authoritatively understand the position of the Lord and His devotees. A devotee like Nārada Muni is addressed as suvrata. Su means “good,” and vrata means “vow.” Thus the word suvrata refers to a person who has nothing to do with the material world, which is always bad. One cannot understand anything spiritual from a materialistic scholar puffed up with academic knowledge. As stated in Bhagavad-gītā (18.55), bhaktyā mām abhijānāti: one must try to understand Kṛṣṇa by devotional service and from a devotee. Therefore Yudhiṣṭhira Mahārāja was quite right in wanting to learn further about Prahlāda Mahārāja from Śrī Nārada Muni.