"Jesus' essential call was to plant churches. Virtually all the great evangelistic challenges of the New Testament are basically calls to plant churches, not simply to share the faith. The 'Great Commission' (Matt. 28:18-20) is not just a call to 'make disciples' but to 'baptize'. In Acts and elsewhere, it is clear that baptism means incorporation into a worshiping community with accountability and boundaries (cf. Acts 2:41-47). The only way to be truly sure you are increasing the number of Christians in a town is to increase the number of churches. Why? Much traditional evangelism aims to get a 'decision' for Christ. Experience, however, shows us that many of these 'decisions' disappear and never result in changed lives. Why? Many, many decisions are not really conversions, but often only the beginning of a journey of seeking God. (Other decisions are very definitely the moment of a 'new birth,' but this differs from person to person.) Only a person who is being 'evangelized8 in the context of an on-going worshiping and shepherding community can be sure of finally coming home into vital, saving faith. This is why a leading missiologist like C. Peter Wagner can say, 'Planting new churches is the most effective evangelistic methodology known under heaven.'"
—Tim Keller, "Why Plant Churches" (pdf)