CC Madhya 22.64
‘uttama’, ‘madhyama’, ‘kaniṣṭha’ — śraddhā-anusārī
“A faithful devotee is a truly eligible candidate for the loving service of the Lord. According to one’s faith, one is classified as a topmost devotee, an intermediate devotee or an inferior devotee.
The word śraddhāvān (faithful) means understanding Kṛṣṇa to be the summum bonum — the eternal truth and absolute transcendence. If one has full faith in Kṛṣṇa and confidence in Him, one becomes eligible to discharge devotional service confidentially. According to one’s faith, one is a topmost, intermediate or inferior devotee.