CC Madhya 19.136

prabhu kahe, — śuna, rūpa, bhakti-rasera lakṣaṇa
sūtra-rūpe kahi, vistāra nā yāya varṇana
Word for word: 
prabhu kahe — Śrī Caitanya Mahāprabhu spoke; śuna — please listen; rūpa — My dear Rūpa; bhakti-rasera — of the transcendental mellows in devotional service; lakṣaṇa — the symptoms; sūtra-rūpe — in the form of a synopsis; kahi — I shall explain; vistāra — the whole breadth; — not; yāya — is possible; varṇana — description.
Translation: 
Śrī Caitanya Mahāprabhu said, “My dear Rūpa, please listen to Me. It is not possible to describe devotional service completely; therefore I am just trying to give you a synopsis of the symptoms of devotional service.