Narada Muni advised him (Vyasadeva) to write about the activities of the Supreme Personality of Godhead. Therefore Vyasadeva began writing Srimad-Bhagavatam

Expressions researched:
"advised him to write about the activities of the Supreme Personality of Godhead. Therefore Vyāsadeva began writing Śrīmad-Bhāgavatam"

Sri Caitanya-caritamrta

CC Madhya-lila

Even after writing many Vedic literatures, Vyāsadeva felt very morose. Therefore his spiritual master, Nāradadeva, told him that he could be happy by writing about the activities of the Supreme Personality of Godhead. Up to that time, Śrīla Vyāsadeva had written the karma-kāṇḍa and jñāna-kāṇḍa sections of the Vedas, but he had not written about upāsanā-kāṇḍa, or bhakti. Thus his spiritual master, Nārada, chastised him and advised him to write about the activities of the Supreme Personality of Godhead. Therefore Vyāsadeva began writing Śrīmad-Bhāgavatam.

CC Madhya 22.19, Translation and Purport

“‘When pure knowledge is beyond all material affinity but is not dedicated to the Supreme Personality of Godhead [Kṛṣṇa], it does not appear very beautiful, although it is knowledge without a material tinge. What, then, is the use of fruitive activities—which are naturally painful from the beginning and transient by nature—if they are not utilized for the devotional service of the Lord? How can they be very attractive?’

This is a quotation from Śrīmad-Bhāgavatam (SB 1.5.12). Even after writing many Vedic literatures, Vyāsadeva felt very morose. Therefore his spiritual master, Nāradadeva, told him that he could be happy by writing about the activities of the Supreme Personality of Godhead. Up to that time, Śrīla Vyāsadeva had written the karma-kāṇḍa and jñāna-kāṇḍa sections of the Vedas, but he had not written about upāsanā-kāṇḍa, or bhakti. Thus his spiritual master, Nārada, chastised him and advised him to write about the activities of the Supreme Personality of Godhead. Therefore Vyāsadeva began writing Śrīmad-Bhāgavatam.