How does the human body illustrate the body of Christ?
The human body is one unified organism with many members—hands, feet, eyes, ears—all operating together from a central nervous system. Likewise, the body of Christ is one body made of many different people from every culture, yet united as one in Christ when saved by the same power and gospel.
Les explains that Paul, not Jesus or Peter, speaks of the body of Christ. In verse 12 Paul uses the human body as an illustration: the body is one, but it has many members, and all the members of that one body, being many, are one body. Hands, feet, eyes, and ears all operate from a central nervous system and a central place of thinking, yet they function as one. So also is Christ, meaning the body of Christ is made up of many different people—rich and poor, black and white, from all around the world. They are all different and have their own cultures, but if they have been saved by the same power and the same gospel, they are one in Christ. Les illustrates this by saying believers could go to the Philippines and feel at home with born-again children of God, because they are one in Christ. He then raises the crucial question of how one enters this living organism called the body of Christ, pointing to verse 13.
For as the body is one, and hath many members, and all the members of that one body, being many, are one body: so also is Christ.