Although preaching is not meant for a maha-bhagavata, a maha-bhagavata can descend to the platform of madhyama-bhagavata just to convert others to Vaisnavism. Actually a maha-bhagavata is fit to spread Krsna consciousness, but he does not distinguish where Krsna consciousness should be spread from where it should not. He thinks that everyone is competent to accept Krsna consciousness if the chance is provided. A neophyte and an intermediate devotee should always be eager to hear the maha-bhagavata and serve him in every respect. The neophyte and intermediate devotees can gradually rise to the platform of uttama-adhikari and become first-class devotees.

From Srila Prabhupada’s purport to CC Madhya 16.74