CC Madhya-lila 23.005 - BRS 1.03.001
Sri Caitanya-caritamrta
CC Madhya-lila
CC Madhya 23.5, Translation and Purport:
“"When devotional service is executed on the transcendental platform of pure goodness, it is like a sun-ray of love for Kṛṣṇa. At such a time, devotional service causes the heart to be softened by various tastes, and one is then situated in bhāva (emotion)."
This verse is found in the Bhakti-rasāmṛta-sindhu (1.3.1).