John Piper:

May we never lose sight of this one phrase: “Brought near by the blood of Christ” (Ephesians 2:13). Brought near to God and therefore brought near to each other. By the blood. By the cross.

Ponder this implication of “by the blood.” Paul says in Galatians 6:14 — and I hope we say with him — “Far be it from me to boast except in the cross of our Lord Jesus Christ.” Boast only in the cross. Does this not mean, among other things, that we want the meaning and the worth and the beauty and the power of the cross of Christ to be seen and loved because of the way we live?

And if one design of the cross of Christ is to reconcile alienated ethnic groups to each other by reconciling them to God in Christ, then will we not display and magnify the cross of Christ better by more and deeper and sweeter ethnic diversity and harmony in our corporate and personal lives? If Christ died — mark this, died! — to make the church a diverse, reconciled body of Jew and Gentile — “red and yellow, black and white,” and every shade and shape in between — then to glory in the cross is to glory in the display of the fruit of that cross.

Bloodlines: Race, Cross and the Christian, (Wheaton: Crossway, 201), 126-7.