CC Madhya 22.150
tan-mayī yā bhaved bhaktiḥ
iṣṭe — unto the desired object of life; svā-rasikī — appropriate for one’s own original aptitude of love; rāgaḥ — attachment; parama-āviṣṭatā — absorption in the service of the Lord; bhavet — is; tat-mayī — consisting of that transcendental attachment; yā — which; bhavet — is; bhaktiḥ — devotional service; sā — that; atra — here; rāgātmikā-uditā — called rāgātmikā, or spontaneous devotional service.
“ ‘When one becomes attached to the Supreme Personality of Godhead according to one’s natural inclination to love Him and is fully absorbed in thoughts of the Lord, that state is called transcendental attachment, and devotional service according to that attachment is called rāgātmikā, or spontaneous devotional service.’
This verse is found in the Bhakti-rasāmṛta-sindhu (1.2.272).