There's a distinct contrast in Ephesians 2:1-10 between the then and the now. Once dead, walking in sin, children of wrath, sons of disobedience. Now alive in Christ, raised up, seated with Christ in heavenly places. It's a reminder of where we've come from and where we are - and why: By grace, through faith. "And this is not your own doing; it is the gift of God" Ephesians 2:8, ESV. We have nothing to boast about, we could have done none of it without God.
Ephesians 2:11-22 carries a common theme of Paul's writings, the common salvation of both Jew and Gentile. He points out that before Christ, the Gentiles were separate from Go and His promises, "having no hope and without God in the world." But then points out that Jesus destroyed that division, "that he might create in himself one new man in place of the two". No, both Jew and Gentile follow the same path to God through Jesus. We are joined together, unified on our journey to God. The message of the cross is a message of reconciliation and unification on many levels, not just God to man, but Jew to Gentile as well.
Paul goes beyond just being friends or being nice to each other. He makes a point at several places in this passage to call the Jew and Gentiles together "one". Not two men standing together, but "one new man". Not two bodies of believers walking together, but "one body." It's not a truce or even a treaty, it's a merging of nations into a new nation, "a dwelling place for God". It's a powerful thought and one we would do well to meditate on and pursue.
