The vocabulary of Ephesians is is rich in “house” and “building” words. Most of them show up in a good English translation, but there are several more in the original Greek. At some points, Paul seems almost to be punning on “house” words, or Greek words made from the oik- root.
For example, a key passage in 2:19 says “so then you are no longer strangers and aliens [par-oik-ioi], but you are fellow citizens with the saints and members of the household [oik-eioi] of God.” Not par-oikioi, but oikeioi: That is, you are no longer outside of the home of God, but you are, well, homies. The passage goes on: you homies are
built [ep-oik-odomethentes] on the foundation of the apostles and prophets, Christ Jesus himself being the cornerstone, in whom the whole structure [oik-odome], being joined together, grows into a holy temple in the Lord. In him you also are being built together [sun-oik-odomeisthe] into a dwelling place [kat-oik-eterion] for God by the Spirit.
A couple of times Paul talks about building each other up, and uses oik-words to do so:
4:16 the body builds itself up [oik-odomen] in love;
4:29 only such talk as is good for building up [oik-odomen]
–which is interesting because in English we also “edify” each other, as if we were “edifices.”
More significantly, Paul refers in Ephesians to his own ministry as a stewardship, which is a great word with oik hidden in it: 3:1, “the stewardship [oik-onomian] of God’s grace that was given to me for you.”
And most important of all, Paul twice uses one of these “house” words to refer to God’s all-encompassing plan that is now being decisively carried out in the spread of the gospel. In 1:10 he says that God has made known to us “the mystery of his will, according to his purpose, which he set forth in Christ as a plan [oik-onomia] for the fullness of time, to unite all things in him, things in heaven and things on earth.” And similarly, in 3:9 Paul says that in his own preaching of the unsearchable riches of Christ, he is bringing to light “what is the plan [oik-onomia] of the mystery hidden for ages in God who created all things.”
Ephesians has a different tone and emphasis from Paul’s earlier (and undisputed) letters. Compare it to Romans and Galatians and you notice that he is no longer doing the brisk, hand-to-hand combat or verse-by-verse arguing from Old Testament proofs. He’s no longer arguing about the status of the law, the nomos, as he did in those letters. His mind has not changed, but in Ephesians I think Paul’s thought expands to take in the full implications of the surprising work of God in Christ. If the old covenant was the realm of the law, the new covenant fulfills it by being the realm of the house-law, the wise household ordering of the Jew-Gentile family by the covenant God who is now known to be “the God and Father of our Lord Jesus Christ.” Paul’s thought develops from nomos to oikonomos.