atha daitya-sutāḥ sarve
śrutvā tad-anuvarṇitam
jagṛhur niravadyatvān
naiva gurv-anuśikṣitam
śrī-nāradaḥ uvāca-Śrī Nārada Muni said; atha-thereupon; daitya-sutāḥ-the sons of the demons (the class friends of Prahlāda Mahārāja); sarve-all; śrutvā-hearing; tat-by him (Prahlāda); anuvarṇitam-the statements about devotional life; jagṛhuḥ-accepted; niravadyatvāt-due to the supreme utility of that instruction; na-not; eva-indeed; guru-anuśikṣitam-that which was taught by their teachers.
Nārada Muni continued: All the sons of the demons appreciated the transcendental instructions of Prahlāda Mahārāja and took them very seriously. They rejected the materialistic instructions given by their teachers, Ṣaṇḍa and Amarka.
This is the effect of the preaching of a pure devotee like Prahlāda Mahārāja. If a devotee is qualified, sincere and serious about Kṛṣṇa consciousness and if he follows the instructions of a bona fide spiritual master, as Prahlāda Mahārāja did when preaching the instructions he had received from Nārada Muni, his preaching is effective. As it is said in the Śrīmad-Bhāgavatam (3.25.25):