"The Church is not an exclusive club of privilege, neither is it a place to rest from our labors. We have been brought in so that we may gather others into this Kingdom of Grace."
Chapter 4 of this book includes a discussion of "The Essence of the Local Church in Historical Perspective," and speaks about the traditional reformational marks of the church (word, sacrament, & doctrine) and casts those in light of a missional reading of the four attributes of the church (one, holy, catholic, & apostolic). Then concludes with these thoughts...
"What is the Church? It is the unifying [one], santifying [holy], reconciling [catholic], and proclaiming [apostolic] activity of Jesus Christ in the world. Mission cannot be something separate from or added to the essence of the Church. The essential nature of the local congregation is, in and of itself, mission, or else the congregation is not really a Church."
"Notice that this description is a far cry from saying that 'everything the church does is mission.' What the church does internally with no intention of impacting the world outside of itself is not mission. But when a local congregation understands that it is, by its nature, a constellation of missional activities, and it intentionally lives its life as a missionary body, then it begins to emerge toward becoming the authentic Church of Jesus Christ."