What is the mystery of the body of Christ?
It is the mystery of Christ and the church (Eph. 5: 32).
When you receive the Lord Jesus Christ as your Saviour, the Holy Spirit baptizes you into the body of Christ (1 Cor. 12:13).  This is not the water baptism the believer goes through after he receives the Lord Jesus Christ as his Saviour (Acts 16: 30-33).  Rather, this is the baptism by the Holy Spirit into the literal death, burial and resurrection of the Lord Jesus Christ (Romans 6: 3-6).

As soon as you get saved, the Holy Spirit performs a spiritual circumcision that cuts the body of the sins of your flesh away from your soul.  Judicially and doctrinally, your body is dead (Romans 6: 7-11), you are crucified with Christ (Galatians 2:20), and your soul is engaged to be married to Lord Jesus Christ (Romans 7:1-6).  Literally, while waiting on the marriage, your soul becomes a part of his body.  Thus, as Eve came forth from Adam’s body to be married to him (Gen. 2:21-25), we will come forth from Christ’s body to be married to him (Revelation 19: 7-9).

Right now, “we are members of his body, of his flesh, and of his bones,” (Eph. 5: 30).  This is not a figurative statement.  It is a fact.  That’s why Paul goes into such a lengthy explanation of our membership in this body in 1 Cor. 12:14-27.  Notice, the context of his description of our location in Christ’s body is Spirit baptism (v. 13).  We are so literally a part of Christ’s body that we have already been raised with him and he has “made us sit together in heavenly places in Christ Jesus,” (Eph. 2: 6).

Because a lot of the modern scholars do not believe this doctrine, they have cut out part of Eph. 5: 30 in their modern translations of the Bible.  They have removed the words “of his flesh, and of his bones.”  Consequently, there are a lot of Christians today who are ignorant of the body of Christ.  Many actually believe that the body of Christ is a wafer that is blessed by a priest and consumed during communion.  They are guilty of “not discerning the Lord’s body,” (1 Cor. 11:29).

Furthermore, if more Christians understood this doctrine they would realize that there is no way they can lose their salvation in the church age.  Once a Christian has already been raised into heavenly places in Christ Jesus and has been put into the body of Jesus Christ, God is not going to kick him out of Heaven and amputate a part of his own Son’s body to send that soul to hell.

It is because of our position in Christ that we are able to fulfill the command of Hebrews 4:16, which says, “Let us therefore come boldly unto the throne of grace, that we may obtain mercy, and find grace to help in time of need.”  Our entrance into the throne room of God is made possible by the fact that we are seated with Christ at the right hand of God Almighty.