Well, the OP reminded me of God's peace plan for the world revealed in Ephesians:
EPH 2:11-12, “Therefore, remember that formerly you who are Gentiles by birth and called “uncircumcised” by those who call themselves “the circumcision” (that done in the body by the hands of men)—remember that at that time you were separate from Christ, excluded from citizenship in Israel and foreigners to the covenants of the promise, without hope and without God in the world.
This is a flashback to before the salvation described in v. 7b-10, referring to all non-Jews (which brought forward includes Muslims), who are called “uncircumcised” by way of denoting the separation of Israel from the rest of humanity because of the laws promulgated by Moses. Physical circumcision signified obedience of the law for Jews, but for Paul it was a sign of faith and the righteousness of Christ that is imputed or credited to believers in Christ (Rom. 3:21-22, 4:3-24), including Gentiles, who had been separate from both the Old and New Covenants and thus without hope and without God in the world (except for what could be discerned from creation and conscience per RM 1:20 & 2:14-15).
EPH 2:13-17, “But now in Christ Jesus you who once were far away have been brought near through the blood of Christ. For he himself is our peace, who has destroyed the barrier, the dividing wall of hostility, by abolishing in his flesh the law with its commandments and regulations. His purpose was to create in himself one new man out of the two, thus making peace, and in this one body to reconcile both of them to God through the cross, by which he put to death their hostility. He came and preached peace to you who were far away and peace to those who were near.”
“In CJ” was the key phrase in Eph. 1, meaning “because of saving faith” the Gentiles are no longer separate from Jews because of the death of Jesus, which atonement had made moot the separation per two phrases describing the end of separation by fulfilling the reason for the separation: God’s POS was for the Law to prepare the way for the Gospel of salvation for all in Christ. God’s peace plan made possible fellowship with Him and with all people (restating v.15b-16). Christ’s death ended the separation of Jews from others, because God’s POS is for Gentiles as well as for the Jews (through whom Messiah was born).
EPH 2:18-22, “For through him we both have access to the Father by one Spirit. Consequently, you are no longer foreigners and aliens, but fellow citizens with God’s people and members of God’s household, built on the foundation of the apostles and prophets, with Christ Jesus himself as the chief cornerstone. In him the whole building is joined together and rises to become a holy temple in the Lord. And in him you too are being built together to become a dwelling in which God lives by his Spirit.”
“Through him” = “in Christ”, and access to the Father means spiritual sonship and salvation, as in Rom. 8:1-2 & 14-17. “You” refers to Gentiles, and “God’s people” refers to the Jews, who during the OT dispensation were separated by the barrier mentioned in v.14; fellow citizens = the one new man in v.15. The analogy of one government is augmented by that of one family, built on apostolic preaching of the Gospel of Christ and on the prophetic teaching of the purpose of the OT Law of Moses, the foundation of both being salvation via faith in the ministry of Messiah/Christ, who is cited next. The crux of key part of God’s POS is Christ’s atonement. The analogies of one government and family are augmented by that of one edifice, which expands as new souls convert to faith in Christ and is deemed holy because each member is indwelt by the Holy Spirit per v.18. As in v.19, “you” refers to the Gentiles, who once were dependent on general revelation for salvation but now are joined with the Jews and the OT by the Holy Spirit as in v.18, which indicates the NT.
EPH 3:1-6, “For this reason I, Paul, the prisoner of Christ Jesus for the sake of you Gentiles—surely you have heard about the administration of God’s grace that was given to me for you, that is, the mystery made known to me by revelation, as I have already written briefly. In reading this, then, you will be able to understand my insight into the mystery of Christ, which was not made known to men in other generations as it has now been revealed by the Spirit to God’s holy apostles and prophets.”
This epistle should be read with Colossians, which refers to Paul being in chains (Col. 4:3&18). Paul’s assignment is recorded in Acts 9:15-16. Although his focus was the Gentiles, Jews were not excluded per Acts 28:17-23. This mystery was described in Eph. 2:13-22 and is mentioned also in Rom. 11:25 & 16:25 as well as in Colossians. The phrase “as I have already written briefly” could mean “as I have just written”, referring yet a third time to Eph. 2:13-22, which statement is paralleled by Rom. 16:25 & Col. 1:26. Rom. 16:26 indicates that Paul has the writings of the OT prophets in mind, as Jesus explained per Luke 24:45-47.
EPH 3:7-9, “I became a servant of this gospel by the gift of God’s grace given me through the working of his power. Although I am less than the least of all God’s people, this grace was given me: to preach to the Gentiles the unsearchable riches of Christ, and to make plain to everyone the administration of this mystery, which for ages past was kept hidden in God, who created all things.”
This reiterates v. 2. The reference to “the working of his power” is vague, but it might refer to the “Damascus Road” (cf. the comment regarding Eph. 1:1). Regarding “the unsearchable riches of Christ”, see the comment on Eph. 1:1&10. Riches will be mentioned again in Eph. 3:16 (cf. Col. 1:27, Rom. 9:23 & 11:33). “Everyone” must include the Jews, and “administration” must include revelation and explanation of the mystery (cf. Eph. 1:9-10 & 2:11-22).
EPH 3:10-11, “His intent was that now, through the church, the manifold wisdom of God should be made known to the rulers and authorities in the heavenly realms, according to his eternal purpose which he accomplished in Christ Jesus our Lord.”
“Intent” refers to the mystery in v.4-9, and “now” means now revealed as in v.5. “Church” refers to the body of Christ in 1:22-23 (cf. Col.1:24). “Wisdom of God” = the Gospel (1Cor. 1:17-24 & 2:7). This concept is found in Eph. 1:21 & echoed in EPH 6:12 & COL 1:16. The “eternal purpose” or POS was introduced in Eph. 1:9-10.