God provides any believer who seeks to grow spiritually all that he needs to do so. God has provided the believer many wonderful things. Some of those are to be utilized for spiritual growth. The Holy Spirit, the Word of God and spiritually gifted teachers are three of the primary provisions for our spiritual growth. We need and rely on all three of these provision.
The Spirit enables to clearly see the truth and apply it. The Word is the spiritual food to be assimilated and applied. The teacher and/or pastor-teacher is the man who God has spiritually gifted to teach the Word of God. This is not to say that we cannot study and learn on our own, we can, but we are limited. Pastor-teachers were give by Christ to his church to equip believers for service and build up the body of Christ (Eph. 4:11).