CC Madhya 8.190
vrīḍā-kuñcita-locanāṁ viracayann agre sakhīnām asau
kaiśoraṁ saphalī-karoti kalayan kuñje vihāraṁ hariḥ
vācā — by speech; sūcita — revealing; śarvarī — of the night; rati — in amorous pastimes; kalā — of the portion; prāgalbhyayā — the impudence; rādhikām — Śrīmatī Rādhārāṇī; vrīḍā — from shame; kuñcita-locanām — having Her eyes closed; viracayan — making; agre — before; sakhīnām — Her friends; asau — that one; tat — of Her; vakṣaḥ-ruha — on the breasts; citra-keli — with variegated pastimes; makarī — in drawing dolphins; pāṇḍitya — of cleverness; pāram — the limit; gataḥ — who reached; kaiśoram — adolescence; sa-phalī-karoti — makes successful; kalayan — performing; kuñje — in the bushes; vihāram — pastimes; hariḥ — the Supreme Personality of Godhead.
“ ‘Thus Lord Śrī Kṛṣṇa spoke of the sexual activities of the previous night. In this way He made Śrīmatī Rādhārāṇī close Her eyes out of shyness. Taking this opportunity, Śrī Kṛṣṇa painted various types of dolphins on Her breasts. Thus He became a very expert artist for all the gopīs. During such pastimes, the Lord enjoyed the fulfillment of His youth.’ ”
This quotation is also found in the Bhakti-rasāmṛta-sindhu (2.1.119).