To those who believed in His name, He gave the right to become children of God – children born not of natural descent, nor of human decision or a husband's will, but born of God. (John ,13 NIV)
What, in the thought of God do Christians exist for? What does the Church exist for? There is only one answer. The existence and the function is to be an expression of Christ. There is nothing less and nothing more than that. Christ is the Alpha and the Omega, the beginning and the end, and all between! Let that be the starting point; let that be the governing rule and reality in all matters of life and work, and see at once the nature and vocation of the Church. This vast, incomprehensible heavenly system, of which Christ is the personal embodiment, touches every detail of life, personally and collectively. But remember only the Holy Spirit sees and knows how it is so; hence, as at the beginning, there has to be an utter submission to and direction by the Lordship of the Holy Spirit. What the bloodstream is to the human body, the Divine Life is to and in "the Church which is His body." What the nerve system is in the physical realm, the Holy Spirit is in the spiritual. Understand all the workings of those two systems in the natural, and you begin to see how God has written His great heavenly principles, first in the person of His Son, and then in His corporate Body.
As an individual believer is the result of a begetting, a conception, a formation, a birth and a likeness, so, in the New Testament, is a true local church. It is a reproduction of Christ by the Holy Spirit. Man cannot make, form, produce or "establish" this. Neither can anyone "join" or "enroll," or make himself or herself a member of this organism. First it is an embryo, and then a "formation" after Christ. So, all talk about "forming New Testament churches" is nonsense. The beginning is in a seeing of Christ.