For he himself is our peace, who has made us both one and has broken down in his flesh the dividing wall of hostility (ESV)
This verse speaks to the human condition so powerfully. It seems that in every generation, and in every land, and in every people group there is some kind of dividing wall of hostility. We reject people because of where they are from, or what color they are, or something that they have done. This was very much the case at the time that Paul wrote these words to the Church at Ephesus. The Jews not only viewed the Gentiles as "dogs," they also had a wall to separate them.
“In Herod’s Temple there was a wall which separated the Court of the Gentiles from the rest of the Temple, and on that wall were inscriptions in Latin and Greek forbidding Gentiles to enter. Josephus spoke of these inscriptions, and in excavations made in 1871 and 1934 two of these inscriptions were found. They read: “No foreigner may enter within the barricade which surrounds the sanctuary and enclosure. Anyone who is caught doing so will have himself to blame for his ensuing death.”
- R. Kent Hughes. Ephesians: The Mystery of the Body of Christ. Crossway Books: Wheaton, IL, page 92.