Srimad Bhagavatam Canto 02, Chapter 09, Text 42

 SB 2.9.42

mayam vividisan visnor
mayesasya maha-munih
maha-bhagavato rajan
pitaram paryatosayat
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
Narada very much pleased his father and desired to know all about the energies of Visnu, the master of all energies, for Narada was the greatest of all sages and greatest of all devotees, O King.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
Lord Brahma, being the creator of all living beings in the universe, is originally the father of several well-known sons, like Daksa, the catuh-sanas, and Narada. In three departments of human knowledge disseminated by the Vedas, namely fruitive work (karma-kanda), transcendental knowledge (jñana-kanda) and devotional service (upasana-kanda), Devarsi Narada inherited from his father Brahma devotional service, whereas Daksa inherited from his father fruitive work, and Sanaka, Sanatana, etc., inherited from their father information about jñana-kanda, or transcendental knowledge. But out of them all, Narada is described here as the most beloved son of Brahma because of good behavior, obedience, meekness and readiness to render service unto the father. And Narada is famous as the greatest of all sages because of his being the greatest of all devotees. Narada is the spiritual master of many famous devotees of the Lord. He is the spiritual master of Prahlada, Dhruva and Vyasa, down to the forest animal hunter Kirata. His only business is to turn everyone to the transcendental loving service of the Lord. Therefore all these features of Narada make him the dearmost son of his father, and all this is due to Narada’s being a first-class devotee of the Lord. The devotees are always anxious to know more and more about the Supreme Lord, the master of all energies. As confirmed in the Bhagavad-gita (10.9):
mac-citta mad-gata-prana
 bodhayantah parasparam
kathayantas ca mam nityam
 tusyanti ca ramanti ca
The Supreme Lord is unlimited, and His energies are also unlimited. No one can know them completely. Brahmaji, being the greatest living entity within this universe and being directly instructed by the Lord, must know more than anyone within this universe, although such knowledge may not be complete. Thus it is the duty of everyone to ask about the unlimited Lord from the spiritual master in the disciplic succession of Brahma, which descends from Narada to Vyasa, from Vyasa to Sukadeva and so on.
Srimad Bhagavatam Canto 02, Chapter 09, Text 41
Srimad Bhagavatam Canto 02, Chapter 09, Text 43