Upon examining ten different Bible translations, the only one we found that used the word "races" was the Today's English Version (TEV).  Most Bibles simply use the word "both," while the New Revised Standard Version uses "both groups." It reads, "and might reconcile both groups to God in one body through the cross, thus putting to death that hostility through it."

But the question remains:  Who are the "both groups," and what is the "hostility"?

In the book of Ephesians, Paul is writing to Gentile converts to Christianity. ("Gentile" was the name given to any people or nation of non-Jewish faith.) Jews and non-Jews (Gentiles) are the two groups of people discussed in the second chapter. These are not two races of people. The descendants of Jacob were the original Israelites, and converts to Judaism included people from many different backgrounds.

After Adam sinned, all of humanity were condemned to eternal death. When God blessed Abraham, because of his faith and obedience, He promised that through Abraham, Isaac, and Jacob, "all peoples on earth will be blessed."  (Genesis 12:3, 22:18, 28:14) God gave Jacob the name Israel (Gen. 35:10). He made Jacob's descendants, the nation of Israel, a chosen people. God made the Law Covenant with Israel and if they kept the Law perfectly, they could escape the Adamic condemnation and obtain eternal life.  At that time the Jewish people were the only people in covenant relationship with God.

The Israelites, also known as the "circumcision" (Ephesians 2:11) were instructed to keep separate from non-Israelites. They were neither to make treaties nor intermarry with people of other nations.  (Exodus 34:12, 15, 16)  The Jewish people realized their covenant relationship with God gave them favor over other nations, and this led to "enmity" or "hostility" between them and Gentiles. 

However, Israel could not keep the law perfectly, which meant they were still under condemnation to death. This was a lesson God wanted them to learn. The sin offerings prescribed under the law only temporarily justified the Israelites from their sins, because those sin offerings were only a picture of the great sacrifice of Jesus, which God had planned.

Since sin had entered by a perfect man, Adam, there needed to be another perfect man to die in his place to satisfy justice. Jesus was "holy, blameless, pure, set apart from sinners."  (Hebrews 7:16) Therefore, when Jesus was crucified on the cross, it was by means of his sacrifice that both Jew and Gentile could receive forgiveness from their sins. They were both reconciled unto God. Colossians 1:20, “And, having made peace through the blood of his cross, by him to reconcile all things unto himself;…”

"Through the gospel, the Gentiles are heirs together with Israel, members together of one body, and sharers together in the promise in Christ Jesus."  (Ephesians 3:6)