CC Madhya 2.83

kahibāra kathā nahe,kahile keha nā bujhaye,
aiche citra caitanyera raṅga
sei se bujhite pāre,
caitanyera kṛpā yāṅre,
haya tāṅra dāsānudāsa-saṅga
Synonyms: 
kahibāra kathā nahe — not a subject matter to describe freely; kahile — if spoken; keha — someone; bujhaye — not understands; aiche — in that way; citra — wonderful; caitanyera — of Śrī Caitanya Mahāprabhu; raṅga — pastimes; sei se — whoever; bujhite — to understand; pāre — is able; caitanyera — of Lord Śrī Caitanya Mahāprabhu; kṛpā — the mercy; yāṅre — unto whom; haya — becomes; tāṅra — His; dāsa-anudāsa-saṅga — association with the servant of the servant.
Translation: 
Such topics are not to be discussed freely because if they are, no one will understand them. Such are the wonderful pastimes of Śrī Caitanya Mahāprabhu. Unto one who is able to understand, Śrī Caitanya Mahāprabhu has shown mercy by giving him the association of the servant of His own servant.
Purport: 

An ordinary person cannot understand the transcendental ecstasies in the mode of Śrīmatī Rādhārāṇī. Unfit persons who try to understand them are perverted into the sahajiyā, bāula and other sampradāyas. Thus the teachings are perverted. Even learned scholars in the academic field cannot understand the transcendental bliss and ecstasy exhibited by Śrī Caitanya Mahāprabhu and His pure devotees. One must be fit to understand the purport of Śrī Caitanya Mahāprabhu’s activities.