It is the invisible spiritual body of Jesus Christ. This invisible body consists of the combined believers in our Divine Saviour. It can almost be reduced to a single sentence. Jesus Christ is the Son of God and if we confess His name and repent of our sins and obey Him in Christian Baptism, we become a constituent part of the body of Christ. Guilt is removed by forgiveness.
Uncertainty is replaced by abundance, and death is overcome by resurrection and immortality.
The background for this truth is the Bible. The Old Testament is Christ concealed in prophecy. The New Testament is Christ revealed in the inspired account. They were not satisfied to be led through the wilderness by the hand of God whose heavens declared His glory and whose firmament showed forth His handiwork. They wanted something which would satisfy the vanity of the flesh and the materialistic lust of the eye.