SB 10.8.47

pitarau nānvavindetāṁ
 kṛṣṇodārārbhakehitam
gāyanty adyāpi kavayo
 yal loka-śamalāpaham
Word for word: 
pitarau — the actual father and mother of Kṛṣṇa; na — not; anvavindetām — enjoyed; kṛṣṇa — of Kṛṣṇa; udāra — magnanimous; arbhaka-īhitam — the childhood pastimes He performed; gāyanti — are glorifying; adya api — even today; kavayaḥ — great, great sages and saintly persons; yat — which is; loka-śamala-apaham — by hearing of which the contamination of the whole material world is vanquished.
Translation: 
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.
Purport: 

Kṛṣṇa actually took birth from the womb of Devakī, but just after His birth He was transferred to the home of mother Yaśodā. Devakī could not even have Kṛṣṇa suck her breast. Therefore Parīkṣit Mahārāja was astonished. How had mother Yaśodā and Nanda Mahārāja become so fortunate that they enjoyed the complete childhood pastimes of Kṛṣṇa, which are still glorified by saintly persons? What had they done in the past by which they were elevated to such an exalted position?