When did the Body of Christ come into existance?
The Body of Christ did not come into existence until after Paul’s salvation. A careful reading of Romans 16:25-26; Ephesians 3:1-6; Ephesians 2:11-12; and Galatians 1:11-12 will establish this fact for us.
This passage is sometimes used to support that Paul's gospel was part of the prophetic program of God. However, Romans 16:25-26 does not mean that the Gospel of the Grace of God was revealed in Old Testament times by Old Testament prophecies. A literal rendering of verse 26 is "the prophetic Scriptures" which refer to the revelation given to Paul and the inspiration of those words which became Scripture.
1 Cor. 14:37 If any man think himself to be a prophet, or spiritual, let him acknowledge that the things that I write unto you are the commandments of the Lord.
Paul's words which became Scripture are actually the Scriptures of the prophets. They were noted just as the above verse states. The prophet acknowledged what Paul said was Scripture, hence, the revelation was the Scriptures (identified) of the prophets. This passage explains the Divine inspiration of Paul's writings, not that they were part of prophecy. This principle is critical to understand. The mystery then was not part of prophecy, it was a secret. The prophets acknowledged what Paul communicated was part of Scripture, even though it was not part of prophecy!