CC Madhya 23.40
antar-vāṇibhir apy asya
mudrā suṣṭhu su-durgamā
dhanyasya — of a most fortunate person; ayam — this; navaḥ — new; premā — love of Godhead; yasya — of whom; unmīlati — manifests; cetasi — in the heart; antar-vāṇibhiḥ — by persons well versed in the śāstras; api — even; asya — of him; mudrā — symptoms; suṣṭhu — exceedingly; su-durgamā — difficult to understand.
“ ‘Even a most learned scholar cannot understand the activities and symptoms of an exalted personality in whose heart love of Godhead has awakened.’
This verse is also found in the Bhakti-rasāmṛta-sindhu (1.4.17).