CC Antya 9.151

caitanya-caritra ei parama gambhīra
sei bujhe, tāṅra pade yāṅra mana ‘dhīra’
Word for word: 
caitanya-caritra — behavior of Lord Caitanya; ei — this; parama gambhīra — very grave; sei bujhe — he understands; tāṅra pade — upon His lotus feet; yāṅra — whose; mana — mind; dhīra — sober.
Translation: 
The intentions of Śrī Caitanya Mahāprabhu are so deep that one can understand them only if he has complete faith in service to the lotus feet of the Lord.