CC Madhya 20.380
dharmī kiśora evātra
vayasaḥ — of age; vividhatve — in varieties; api — although; sarva — of all kinds; bhakti-rasa-āśrayaḥ — the shelter of devotional service; dharmī — whose constitutional nature; kiśoraḥ — in the age before youth; eva — certainly; atra — in this; nitya-līlā — of eternal pastimes; vilāsa-vān — the supreme enjoyer.
“ ‘The Supreme Personality of Godhead is eternally enjoying Himself, and He is the shelter of all kinds of devotional service. Although His ages are various, His age known as kiśora [pre-youth] is best of all.’
This verse is found in the Bhakti-rasāmṛta-sindhu (2.1.63).