Although Kṛṣṇa was so pleased with Vasudeva and Devakī that He descended as their son, they could not enjoy Kṛṣṇa’s magnanimous childhood pastimes, which are so great that simply chanting about them vanquishes the contamination of the material world. Nanda Mahārāja and Yaśodā, however, enjoyed these pastimes fully, and therefore their position is always better than that of Vasudeva and Devakī.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
पितरौ नान्वविन्देतां कृष्णोदारार्भकेहितम् । गायन्त्यद्यापि कवयो यल्लोकशमलापहम्
pitarau nānvavindetāṃ kṛṣṇodārārbhakehitam | gāyantyadyāpi kavayo yallokaśamalāpaham
SB 10.8.47