First Corinthians 12:12-13 says, "For even as the body is one and has many members, yet all the members of the body, being many, are one body, so also is the Christ. For also in one Spirit we were all baptized into one body, whether Jews or Greeks, whether slaves or free, and were all given to drink one Spirit."
We have seen that the church comes out of Christ. Now we want to see how the church is one in the Holy Spirit.
The church comes out of Christ. This speaks of its origin. Every Christian possesses a new life. The one life of Christ has become millions of Christians. John 12 speaks of a grain of wheat which falls into the ground and dies and bears much fruit. All the grains which are produced from the one grain have the same essence as the original grain. One grain has become many grains, and the many grains come out of that one grain. How then can the many Christians who possess the same life become the one Body of Christ? This is where the work of the Holy Spirit comes in. The one Christ has become millions of Christians. Now the Holy Spirit baptizes these millions of Christians into one Body. This is the fundamental teaching recorded in 1 Corinthians 12:12-13. The Body is one, yet it is composed of many members. How can the many members become one Body? "In one Spirit we were all baptized into one body." In other words, this Body comes into being through baptism. Through baptism in the Spirit, the many Christians are immersed into one Body. Every Christian is like a piece of stone hewn out of a big rock. The Holy Spirit is like the cement which cements the stones back together to become one rock.
The Body of Christ has two basic principles: First, apart from that which comes out of Christ, there is no Body of Christ; second, apart from the operation of the Holy Spirit, there is no Body of Christ. There must first be the baptism of the Spirit and the infilling of the Spirit; God’s children must all be baptized by the Spirit in order to become the Body. This was what happened at Pentecost in Acts 2. Many had received the Lord’s life and had become His many members. Then the Lord baptized these many members through the Holy Spirit into one Body. Those who know the Lord and the Holy Spirit also will know this one Body. There are many members in the human body, but the head rules over them all through the nerves. Likewise, the Head of the church joins the many members into one Body through the Holy Spirit.
The church is out of Christ, and it is formed into one Body in the Holy Spirit. Christian fellowship and communion should be based on one’s standing in the Body of Christ. We have no relationship other than this relationship. We are not bound together because we are Jews or Greeks. We commune with one another because we are all members of the Body of Christ. Our communion with one another is based on the Body.
There is only one basis for our fellowship in the church—our being fellow members with one another in the Body. We cannot have any fellowship that is based on any other foundation. Any fellowship outside the Body of Christ is a division. Any fellowship that is not as large as the Body, that is in fact smaller than the Body, is not the fellowship of the Body. Any boundary that is different from the boundary of the Body, though it may not contradict the boundary of the Body, is a hindrance to the Body boundary. Such a variation in boundary will always hinder the fellowship of the Body. We cannot accept any fellowship that is different from the Body. We are here to maintain the fellowship of Christians, the fellowship of the Body, not any fellowship that is smaller than the Body.
(New Believers Series: Body of Christ, The #24, Chapter 1, by Watchman Nee)