CC Antya 19.105
antar-vāṇībhir 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; antaḥ-vāṇībhiḥ — by persons well versed in the śāstras; api — even; asya — of him; mudrā — the symptoms; suṣṭhu — exceedingly; su-durgamā — difficult to understand.
“The activities and symptoms of that exalted personality in whose heart love of Godhead has awakened cannot be understood even by the most learned scholar.”
This verse is quoted from the Bhakti-rasāmṛta-sindhu (1.4.17).