At some point during or after his conversion on the road to Damascus, Paul was given a mystery to proclaim to the world, a body of content that was delivered with new clarity to the apostle by the Lord Jesus Himself. This mystery was not some kind of secret knowledge that only an elite few can bear; rather, it was given to Paul in order that he might deliver it to all Christians (Eph. 3:1–3). This mystery, the apostle explains, is “the mystery of Christ” (v. 4).
Paul goes on in the following verses to define the mystery for his readers, but for now let us consider what it means that the apostle understands his mystery as the mystery of Christ or the mystery involving Jesus. Puritan commentator Matthew Henry is helpful here. He writes that “it is called the mystery of Christ because it was revealed by him, and because it relates so very much to him.” Galatians 1:11–12 shows that it was the revelation of Jesus Christ that put this mystery into Paul’s stewardship. Therefore, our Savior revealed it to His apostle by the Holy Spirit. Yet the mystery not only was given by Christ but is also about Christ. Essentially, the mystery is equivalent to the gospel, that good news of salvation, declaring that men and women can be forgiven of their sins and made full citizens of the kingdom of God when they repent and trust in Christ Jesus alone for salvation. Throughout the New Testament, we see the gospel described as “the gospel of Jesus Christ” or “the gospel of our Lord Jesus” — the good news of who He is and what He has done for His people (Mark 1:1; 2 Thess. 1:8).
Given the definition of the term mystery as something that was once veiled but is now plainly revealed, to call the gospel a mystery emphasizes the newness of the message that came when the Son of God became incarnate two thousand years ago. It is not as if the gospel was wholly unknown to the old covenant saints, for they were set right with the Father in the same way that we are — through faith alone (Gen. 15:6). Yet the knowledge the old covenant saints had of the gospel was faint in comparison to the glorious revelation delivered by Jesus through His new covenant apostles and prophets. What they saw only in part we now see more fully, and we are assured that God’s people include the elect of all nations (Eph. 3:6).