Why were the Jews separated from the Gentiles in the Old Testament?
God had mandated that Israel remain a separated people from the Gentiles, not because the Jews were bigoted or proud. That separation was required whenever they had knowledge of God and His word, and when they lost it, God's judgment fell, as in the Balaam incident.
Les teaches that all the way up through the Old Testament, Israel was a separated people anytime they had a knowledge of God and His word. When they lost that separation, God's judgment fell. He points to Balaam the false prophet: Balak, king of Moab, could not defeat or curse Israel militarily, so Balaam advised putting Moabite women before Jewish young men to seduce them. It worked, and 23,000 Jews were put to death because they had lost their separated character. Les explains this was not because the Jew had become bigoted and proud; God had mandated that they stay separated from the Gentiles. He also notes the Acts account where Paul says the Lord sent him far hence unto the Gentiles, and the Jewish multitude rioted at the very word “Gentile.”