Here Paul speaks of this mystery that he wants to make certain his readers understand. But the mystery is not actually anything new or hidden. It is the message he has been sharing throughout this letter that on the basis of Gods mercy, God is at work saving people both Jews and Gentiles both on that same basis. And this remains true today. Everyone who calls on the name of the Lord Jesus will be saved on precisely that same basis, the mercy and grace of God in Christ Jesus.