What was Israel's original role toward the Gentiles in the Old Testament?

Les explains that back in the Old Testament, the promise was that Israel, every Jew, could be a priest of God to bring the Gentiles to a knowledge of their Jehovah God. But Israel missed it. That did not stop God. Instead of taking the whole nation of Israel, God raised up one other little Jew, Saul of Tarsus, a renegade zealous for the law, and saved him by grace on the road to Damascus. God told Saul He would send him far hence to the Gentiles. Saul would also go to the Jew, but he was primarily converted as the apostle of the Gentiles. Paul then shows that Israel’s stumbling did not mean God was through with His covenant people. Through their fall, salvation came to the Gentiles, but under a whole different format.