In doing this, he describes the church in three word-pictures.
1. The Multi-Ethnic Church As A Homeland (19a). “So then you are no longer strangers and aliens, but you are fellow citizens with the saints…”
Believing Gentiles are no longer outcasts, cut off from God’s people, (‘refugees’ – O’Brien), but are ‘fellow citizens with the saints,’ standing on equal ground in Christ! Christians are citizens of a homeland that trumps our ethnic origins; the banner of the cross outweighs whatever flag our home nation flies. Our identity is first and foremost in Christ.
But our citizenship is in heaven... Philippians 3:20, ESV2. The Multi-Ethnic Church As A Family (19b-20). “and members of the household of God, built on the foundation of the apostles and prophets, Christ Jesus himself being the cornerstone…”
In Christ, believing Gentiles and Jews are brothers and sisters – part of the same family: the family of God! Members of his household! We have been much more than forgiven; welcomed to the table of the King as his sons and daughters through Jesus Christ!
Paul goes on to say that this household to which we belong is built on the foundation of the ‘apostles and prophets,’ both of which speak and proclaim the word of God. Thus, the church is built on the foundation of the preached gospel. And the cornerstone is Christ himself. This unified church rests on Jesus and the anointed message of his death and resurrection.
The stone that the builders rejected has become the cornerstone.  This is the LORD's doing; it is marvelous in our eyes. Psalm 118:22-23, ESV3. The Multi-Ethnic Church As A Temple (21-22). “in whom the whole structure, being joined together, grows into a holy temple in the Lord. In him you also are being built together into a dwelling place for God by the Spirit.”
Not only is the church a homeland and a family; the saints have also become the temple of God in Christ!
Holy. Sanctified by Christ’s blood, this multi-ethnic structure is ‘holy’ and set apart to the Lord, who fills his house!
Growing. The house is not yet complete, for there are others who will believe and be joined to the structure. Internal building is also taking place as the ‘living stones’ are growing stronger through our ministry to one another in the church.
Joined Together. These living stones are ‘joined together’ and are ‘being built together.’ Now Gentiles are ‘not only NOT forbidden from entering the temple, but are part of the temple in Christ’ (Stott). This is not individualistic work, but corporate work. We are members of one another (Eph 4:25; Rom 12:5).
Paul again emphasizes community by pointing to the Trinity (as he did in verse 18). Verse 22 says that in him (Christ) the church is being built together as a dwelling place for God (the Father) by the (Holy) Spirit. Just as the Three Persons of the One God are unified in fellowship, intimacy and love, so is the church!
As you come to him, a living stone rejected by men but in the sight of God chosen and precious,  you yourselves like living stones are being built up as a spiritual house, to be a holy priesthood, to offer spiritual sacrifices acceptable to God through Jesus Christ.  For it stands in Scripture: “Behold, I am laying in Zion a stone, a cornerstone chosen and precious, and whoever believes in him will not be put to shame.”  So the honor is for you who believe, but for those who do not believe, “The stone that the builders rejected has become the cornerstone,”  and “A stone of stumbling, and a rock of offense.” They stumble because they disobey the word, as they were destined to do.  But you are a chosen race, a royal priesthood, a holy nation, a people for his own possession, that you may proclaim the excellencies of him who called you out of darkness into his marvelous light.  Once you were not a people, but now you are God's people; once you had not received mercy, but now you have received mercy. 1 Peter 2:4-10, ESVAt the cross Christ has accomplished the work of unity for all who are in him. He is building his church as a unified, multi-ethnic body, for his glory!