The body of Christ is a figure used in the New Testament to describe the assembly of God. The body of Christ was formed on the Day of Pentecost, when the Spirit of God was sent down to the earth, and indwelt the believers present, linking them to Christ in heaven. Believers on earth who have the Spirit indwelling them are members of the body (Rom. 12:5). Christ in heaven is the head of the body (Col. 1:18). Christ's mind is to be displayed by His body on earth. The Holy Spirit is the one who directs the members of the body; similar to how the nervous system in the human body works. It is important to understand that the body is not a mere concept. It is a reality!
The Body of Christ.
Present and Eternal Aspects. With one exception, the scripture always speaks of the body of Christ as a present thing. This means that Christians who have died are no longer part of the body of Christ. They are part of the Assembly of God still, but they no longer function on earth. The one exception is Eph. 1:22-23, where Paul speaks of “the assembly, which is his [Christ’s] body, the fullness of him who fills all in all”. In this case it is the eternal aspect of the body, including all members, from Pentecost to the rapture. Here the body is viewed as the complement of the head, similar to how the wife is the complement of the husband.
Universal and Local Aspects. The assembly of God is a universal thing, but its activities are carried out in local gatherings. The local gatherings of the members are called “assemblies” in the New Testament. The local assembly (e.g. in the city of Corinth) is the official gathering of the Body of Christ in that location. These two aspects of the assembly are reflected in the truth of Christ’s body. In 1 Corinthians 12 we get both aspects of the body. In vv.12-13 it is the universal aspect; “all the members of the body, being many, are one body, so also is the Christ… we have all been baptised into one body”. In v.27, Paul brings out that the Corinthians, a local assembly, were the body as well; “now ye are Christ’s body, and members in particular”. It’s not that the entire, universal body of Christ was located in Corinth, but that the local assembly there had “body-character”. While there is only one body, the local assembly is an expression of the whole, and enjoys all the rights and privileges of the universal Church. A simple example has often been used: there is a U.S. Army base in Watertown, NY. I can drive up to the fence and say; “there is the U.S. Army”. I do not mean that the entire U.S. Army is in front of me. That would be impossible because the US Army is not only enormous in size, but distributed all over the world. And yet, what I see before me is an installment of the US Army, which has all the character, privileges, and authority of the whole Army, to act on its behalf. This is true of the local assembly as well. This simple truth is the very ground on which the Church ought to gather for worship and ministry. When the assembly breaks bread at the Lord’s table, this truth is expressed (1 Cor. 10:17).
The Unity of the Body. One of the leading features of the body of Christ is its unity. We are told six times over that “there is one body”; Rom. 12:5; 1 Cor. 10:17; 1 Cor. 12:13; Eph. 2:16; Eph. 4:4; Col. 3:15. Today, the outward unity of the Church is fractured, but the true unity of the body can never be broken. We are to “use diligence” to “keep the unity of the Spirit” (Eph. 4:3); i.e. to practically display the unity of the Body in the earth. We are also to “hold the head” (Col. 2:19); i.e. practically reflect the mind of Christ. We can only do this by submitting to the leading of the Spirit. It takes grace and a lot of effort.
The Body of Christ and the House of God. The body and the house are two very common figures used to describe the Assembly in the New Testament. The ‘body’ is a term used exclusively by the Apostle Paul, while the ‘house’ is a term used by others in addition to Paul. The body carries the thought of unity, and the expression of the desires of the Head (Eph. 1:22-23, 2:14-18, 3:6, 4:4). The house carries the thought of a public witness, and the importance of order (Eph. 2:19-22). Another difference has to do with profession and reality. The body of Christ never takes in any who have not believed the gospel and been sealed with the Spirit of God (Eph. 1:13; 4:4; 1 Cor. 12:13). The house of God on the other hand sometimes includes those who have made a profession of Christ, but do not have genuine faith. This can be seen in the three concentric spheres of Eph. 4:4-6. The inner circle of reality is connected with “one body, one Spirit, one hope”; no unbelievers are there. The second circle is connected with “one Lord, one faith, and one baptism”; but many say “Lord, Lord”, subscribe to “the faith”, and take “baptism” without real faith. This is an important difference to note.