In "Teaching Tips" for this coming Sunday's lesson, Greg Blake writes...

Church membership is envisioned as a call, a dynamic activity. It is not about being a part of a self-justified or self-serving institution. The church exists in the service of its members growing up, maturing into the full stature of Christ. The church, in this vision, is a true center for spiritual discipline and development. Maturing into the full stature of Christ is the call of every baptized Christian, and the church serves the fulfillment of this call.

Source: Galatians and Ephesians: Adult Teacher's Insights, page. 64.