O Nārada, you were taught about the science of God and His transcendental loving service by the Personality of Godhead in His incarnation of Haṁsāvatāra. He was very much pleased with you, due to your intense proportion of devotional service. He also explained unto you, lucidly, the full science of devotional service, which is especially understandable by persons who are souls surrendered unto Lord Vāsudeva, the Personality of Godhead.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
तुभ्यं च नारद भृशं भगवान् विवृद्ध- भावेन साधु परितुष्ट उवाच योगम् । ज्ञानं च भागवतमात्मसतत्त्वदीपं यद्वासुदेवशरणा विदुरञ्जसैव
tubhyaṃ ca nārada bhṛśaṃ bhagavān vivṛddha- bhāvena sādhu parituṣṭa uvāca yogam | jñānaṃ ca bhāgavatamātmasatattvadīpaṃ yadvāsudevaśaraṇā vidurañjasaiva
SB 2.7.19