Ephesians 1:22-23 says, “And God placed all things under [Christ’s] feet and appointed him to be head over everything for the church, which is his body, the fullness of him who fills everything in every way.” When it says here that Christ is filling everything in every way, I take it to mean that he is asserting his rule over everything everywhere in every way (cf. verse 22). Since the church as the body of Christ is this fullness, it means that the rule of Christ over all things is meant to be accomplished and demonstrated through the church as the embodiment of the Son.
The Bible has these things to say about the church as the body of Christ:
1. “For the husband is the head of the wife as Christ is the head of the church, his body, of which he is the Savior” (Ephesians 5:23). The body does not exist apart from the head. They are inseparably connected. Christ is the head of the church, which he redeemed for himself by his death on the cross. Thus the church functions as the body of Christ – his fullness, or the embodiment of his rule – when we are submitted to his authority and leadership.
2. “After all, no one ever hated his own body, but he feeds and cares for it, just as Christ does the church – for we are members of his body” (Ephesians 5:29-30). As the body of Christ, the church belongs to Christ and is loved by him. He supplies what we need and watches over us. Thus the church functions as the body of Christ – his fullness – when we depend upon his provision and protection.
3. “Let the peace of Christ rule in your hearts, since as members of one body you were called to peace. And be thankful” (Colossians 3:15). Christ is our peace (cf. Ephesians 2:14-16), who unites us together in one body. Thus the church functions as the body of Christ – his fullness – when we practice the peace or unity of Christ.
4. “But in fact God has arranged the parts in the body, every one of them, just as he wanted them to be. If they were all one part, where would the body be? As it is, there are many parts, but one body (1 Corinthians 12:18-20). The church is one body, but has many parts. God designed the church to be diverse, with a variety of spiritual gifts. Thus the church functions as the body of Christ – his fullness – when we accept and appreciate this diversity.
5. “Just as each of us has one body with many members, and these members do not all have the same function, so in Christ we who are many form one body, and each member belongs to all the others” (Romans 12:4-5). The church is one body with many members; therefore, we need one another. In fact, we belong to each other, which is to say that in the church, I am a part of you and you are a part of me. We have a mutual responsibility to one another. Thus the church functions as the body of Christ – his fullness – when we love one another.
Ephesians 4:15-16 tells us what happens when the church acts like the body of Christ that it is: “Instead, speaking the truth in love, we will in all things grow up into him who is the Head, that is, Christ. From him the whole body, joined and held together by every supporting ligament, grows and builds itself up in love, as each part does its work” (Ephesians 4:15-16). In other words, we will grow, be built up and become mature: “until we all reach unity in the faith and in the knowledge of the Son of God and become mature, attaining to the whole measure of the fullness of Christ” (Ephesians 4:13). The church is the fullness of Christ - in which the rule of Christ over all things is accomplished and demonstrated. One day it will attain to what it is; the whole measure of Christ’s fullness will be seen in his body.