Revelation 5:9-10 is a glimpse into the purposes of God in the death of His Son, the Lamb of God, Jesus Christ:
“And they sang a new song, saying, “Worthy are you [referring to the slain and risen Lamb of God] to take the book [that is, the book of history in the last days] and to break its seals; for You were slain, and purchased for God with Your blood men from every tribe and tongue and people and nation. You have made them to be a kingdom and priests to our God; and they will reign upon the earth” (NASB).
The implications here for racial and ethnic harmony in the church are staggering when you let it sink in. The price of God’s securing ethnic diversity in the “priesthood,” and the “kingdom” is the death of His Son. The design of the atonement is racial diversity in the company of the redeemed. Applying and pursuing [racial harmony] is not merely a “social issue.” It is a blood-of-Jesus issue. That is what it cost. And that is how important it is.
Not only that, we can up the ante even more. Notice that in Revelation 5:9 this diversity was purchased “for God.” “You…purchased for God…men from every tribe” (NASB). The issue is not only a blood-of-Jesus issue, it is a glory-of-God issue. Blood-bought racial diversity and harmony is for the glory of God through Christ. It is all aiming at the all-satisfying, everlasting, God-centered, Christ-exalting, experience of many-colored worship.
If the pursuit of ethnic diversity and harmony in the company of the redeemed cost the Father and the Son such a price, should we expect that it will cost us nothing? Or that it will be easy? No, the devil, who hates the glory of God and despises the aims of the cross, will not relent without a fierce battle. To join God in pursuing racial diversity and racial harmony will be costly for you and your church–so costly that many will try it for a while and then give up and walk away from the effort to easier things.
But some will persevere and be found doing their duty when the Master comes. Be among that number, brothers… Read and study and pray and preach and take the risks necessary to sever the root of racism.
John Piper, Brothers, We Are Not Professionals, 207-209