"Do we not all have one Father? Did not one God create us? Why do we profane the covenant of our ancestors by being unfaithful to one another?" — Malachi 2:10
Unity is very important to God. Throughout the Bible God commands faithfulness and love. God makes and upholds covenants with his people, and he calls us to honor these covenants. God sees all human beings as one family, and he expects us also to see each other and treat each other that way.
In the area where I live, for two weeks many churches cover their signs with burlap saying "One Lord, One Church." This acknowledges that Christians have not been as united as they should be. Unfortunately, disunity is not a new sin in the church of Jesus Christ. Already in Malachi's time God's people were breaking faith with each other. Instead of acting like brothers and sisters, they often treated each other like enemies.
Jesus came to unite all people. In God's family "there is no Gentile or Jew, circumcised or uncircumcised, barbarian, Scythian, slave or free, but Christ is all, and is in all" (Colossians 3:11). When Christ has filled someone's heart, that becomes their identity. Having Christ in our heart is deeper than ethnicity because we are all created by the same God and rescued from sin through Jesus Christ.
The church, God's family, is for everyone adopted by God through Jesus Christ. Christians, let us hold tightly to our brothers and sisters and remain united in God's love.