CC Madhya 23.5
kṛd asau bhāva ucyate
śuddha-sattva — by unadulterated goodness; viśeṣa — distinguished; ātmā — whose nature; prema — of love of God; sūrya — like the sun; aṁśu — a ray; sāmya-bhāk — which is similar to; rucibhiḥ — by different tastes; citta — of the heart; masṛṇya — softness; kṛt — which causes; asau — that softness; bhāvaḥ — emotion; ucyate — is called.
“ ‘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).