…by revelation He made known to me the mystery… 5 which in other ages was not made known to the sons of men, as it has now been revealed by the Spirit to His holy apostles and prophets: 6 that the Gentiles should be fellow heirs, of the same body, and partakers of His promise in Christ through the gospel – Eph 3:3, 5-6
What Paul says here is very powerful, and to many people at that time, it was still somewhat controversial. Remember, the religious climate at that time was rather tumultuous. Pagan and emporer worship was widely practiced, Judaism was still a powerful force in Israel, and Christianity was spreading quickly, Jesus having recently been crucified (within 30 years, or so).
What Paul explains here in Ephesians is that God has finally revealed his entire plan: everyone (Jews and Gentiles) have access to salvation.
To the Jews, this was still a sore point. They had always been God’s chosen people, and giving up that status was difficult for many of them. Nevertheless, giving the Gentiles that access is what God’s plan had been all along, and when it was first revealed by the conversion of Cornelius in Acts 10, it finally illuminated the thread that unifies the whole Bible. In other words, the mystery was finally revealed.
The Bible teaches us that God’s plan was in existence before the foundation of the world (Eph 1:4), and when Adam and Eve sinned, our need for that plan became apparent. Their sin separated mankind from God’s presence, and we needed an avenue back to him. That avenue is Christ.
16 Now to Abraham and his Seed were the promises made. He does not say, “And to seeds,” as of many, but as of one, “And to your Seed,”[i]who is Christ. – Galatians 3:16
The promise that Paul refers to here in Galatians is one of three that God made to Abraham. God promised that Abraham would father a great nation, that his descendants would inherit the land of Canaan, and that all nations of the earth would be blessed through his “Seed.” In other words, that last promise referred to one who would be of Abraham’s lineage and would save all nations. As Paul tells us here, that Seed is Christ.
The promise of Christ was made very early on, but it was thousands of years before he came. So, in the meantime, God set up a law. This law was never intended to be a substitute for the salvation in Christ, but was meant to guide Abraham’s descendants in righteous living. In addition to that, it served to teach the Israelites who God is and established prophecies concerning the coming Messiah, the Seed, Christ.
19 What purpose then does the law serve? It was added because of transgressions, till the Seed should come to whom the promise was made… 23 But before faith came, we were kept under guard by the law, kept for the faith which would afterward be revealed. 24 Therefore the law was our tutor to bring us to Christ, that we might be justified by faith. 25 But after faith has come, we are no longer under a tutor. – Gal 3:19, 23-25
The passage above explains why the Law of Moses was given. It was never meant to save us; only Christ’s sacrifice could do that. The Old Law was meant as a bridge to carry us to Christ, and once we’ve made it to him, the bridge has served its purpose.
What Paul talks about in Ephesians 3 (and what Cornelius’s conversion exemplifies) is the fulfillment of the promise that God made to Abraham thousands of years ago: that one would come through his line who would bless all nations of the earth. Christ has come, he has lived a perfect life on this earth, and he has died for every person who has ever existed, including you and me. He has died so that we can live…
Let’s make sure we don’t waste that sacrifice.