CC Madhya 22.68

yaḥ śāstrādiṣv anipuṇaḥ
śraddhāvān sa tu madhyamaḥ
Word for word: 
yaḥ — anyone who; śāstra-ādiṣu — in the revealed scriptures; anipuṇaḥ — not very expert; śraddhāvān — full of faith; saḥ — he; tu — certainly; madhyamaḥ — second-class or middle-class devotee.
Translation: 
“ ‘He who does not know scriptural argument very well but who has firm faith is called an intermediate or second-class devotee.’
Purport: 

This verse appears in the Bhakti-rasāmṛta-sindhu (1.2.18).