From Ephesians by Peter S. Williamson, reflecting on Ephesians 3:4-6
Gentiles welcome. To Christians of the twenty-first century, most of whom are Gentiles, it is hard to grasp the significance of this “mystery.” It seems old news that Gentiles can belong to the people of God. But for the nineteen centuries between the time of Abraham and the time of Christ, only the Jewish people had been the heirs of God’s promises, and these promises distinguished them from all the other peoples of the earth (Deut 7:6–7). It might be possible to think that this is simply Jewish chauvinism on Paul’s part, but that would be mistaken. Jesus himself, when the Canaanite woman sought deliverance for her daughter from a demon, confirms that the Gentiles did not have an equal claim to God’s provision that had been promised to the children of Israel (Matt 15:22–28).
Beginning with the death and resurrection of Jesus and the gift of the Spirit, however, a new age has dawned in which all the peoples of the earth are invited to share in the blessings previously promised to one particular nation. This is the “mystery,” the secret plan of God, that has now been revealed. God always loved and took concern for all peoples of the world (Jon 4:10–11; Acts 14:16–17) and intended from the beginning to bless all nations through Abraham and his descendants (Gen 12:3; 18:18; Gal 3:8–9). Although the prophets spoke on many occasions of God’s future blessings for the nations (e.g., Isa 49:6; 66:18–20), Israel never imagined this would involve making the Gentiles “coheirs,” and “copartners in the promise,” joining them “in the same body.” Israel was chosen, as we Christians have now been chosen, to bring God’s blessing to others. Christians do this by proclaiming the gospel.
The basis of church teaching. Catholic doctrine rests on the apostles’ testimony to what Christ did and taught and what the Holy Spirit revealed to them after Jesus’ death and resurrection, including an understanding of the Old Testament in light of Christ (Dei Verbum 8–9). The apostles’ teaching has been handed on to us in Scripture and Tradition that together “form one sacred deposit of the word of God, entrusted to the Church” (Dei Verbum 10), authoritatively interpreted by the apostles’ successors, the pope and bishops.