The church of God is one and cannot be divided (1 Cor. 1:13a), but the members of the Body of Christ are spread across the earth and cannot physically gather in one place. The problem of geography is the reason that there are many churches in time and space. For the believers to practically gather together, the unique teaching and pattern in the New Testament is that of a local church, a church whose ground is the locality, or the city, in which it is located. No other pattern is presented for the ground of a local church, whether smaller than a city or greater than a city. The New Testament is consistent in its depiction of local churches and in the apostles’ teaching concerning the establishing of local churches. The following article from Shepherding Words clearly shows that the universal Body of Christ is expressed practically as the local church in each city.
Assailing the Ground of Oneness (1): the Genuine Ground of the Church According to the Teaching and Practice of the New Testament