SB 11.2.11

śrī-nārada uvāca
samyag etad vyavasitaṁ
 bhavatā sātvatarṣabha
yat pṛcchase bhāgavatān
 dharmāṁs tvaṁ viśva-bhāvanān
Synonyms: 
śrī-nāradaḥ uvāca — Nārada Muni said; samyak — correctly; etat — this; vyavasitam — determined; bhavatā — by you; sātvata-ṛṣabha — O best of the Sātvata clan; yat — because; pṛcchase — you are asking about; bhāgavatān dharmān — duties toward the Supreme Lord; tvam — you; viśva-bhāvanān — which can purify the entire universe.
Translation: 
Śrī Nārada said: O best of the Sātvatas, you have quite correctly asked about the eternal duty of the living entity toward the Supreme Lord. Such devotional service to the Lord is so potent that its performance can purify the entire universe.
Purport: 

A similar statement was made by Śrī Śukadeva Gosvāmī in the first verse of the Second Canto when he congratulated Parīkṣit Mahārāja for asking about Kṛṣṇa.

varīyān eṣa te praśnaḥ
 kṛto loka-hitaṁ nṛpa
ātmavit-sammataḥ puṁsāṁ
 śrotavyādiṣu yaḥ paraḥ

“My dear King, your question is glorious because it is very beneficial to all kinds of people. The answer to this question is the prime subject matter for hearing, and it is approved by all transcendentalists.”

Similarly, Śrīla Sūta Gosvāmī congratulated the inquiring sages of Naimiṣāraṇya in the following words:

munayaḥ sādhu pṛṣṭo ’haṁ
 bhavadbhir loka-maṅgalam
yat kṛtaḥ kṛṣṇa-sampraśno
 yenātmā suprasīdati

“O sages, I have been justly questioned by you. Your questions are worthy because they relate to Lord Kṛṣṇa and so are of relevance to the world’s welfare. Only questions of this sort are capable of completely satisfying the self.” (Bhāg. 1.2.5)

Nārada will now answer Vasudeva’s inquiry about the process of devotional service. Later, at the end of their conversation, he will reply to Vasudeva’s comments about Vasudeva’s own faulty intentions.