God had chosen to work through His nation of Israel, the Jews, so they could be a light to the Gentiles, the non-Jews. The nation of Israel was at the crossroads of the ancient world. God placed them there to influence all the people traveling through the country.
Moses had let the people in on God’s plan. Deuteronomy 4: 5 “Look, I (Moses) now teach you (Israel) these decrees and regulations just as the Lord my God commanded me, so that you may obey them in the land you are about to enter and occupy. 6 Obey them completely, and you will display your wisdom and intelligence among the surrounding nations. When they hear all these decrees, they will exclaim, ‘How wise and prudent are the people of this great nation!’ 
Israel was Not a Light
God took the Hebrew people to the promised land. They first agreed to follow God’s law but then began to take on the customs of the Gentiles around them. Instead of influencing the other nations and showing who God is, the country of Israel became like the Gentile nations.
God called Isaiah to tell them of a new plan. Since they couldn’t be the light, He would send one that would be the light. Isaiah 42: 6 “I, the Lord, have called you to demonstrate my righteousness. I will take you by the hand and guard you, and I will give you to my people, Israel, as a symbol of my covenant with them. And you will be a light to guide the nations. God gave hope during their failure. He would send a Messiah to carry out His plan.
This is such a sure hope that God has Isaiah repeat the promise three chapters later. Isaiah 49:6 He says, “You will do more than restore the people of Israel to me. I will make you a light to the Gentiles, and you will bring my salvation to the ends of the earth.” God will use the Messiah to restore both the Jews and the Gentiles.
The Gentiles Accept the Light
It was unusual for a devout Jewish man to speak of Gentiles while standing in the Temple. But that was precisely what Simeon did because he knew the prophecies and what God had told him. Luke 2: 30 I have seen your salvation, 31 which you have prepared for all people. 32 He is a light to reveal God to the nations, and he is the glory of your people Israel!”
For Jesus would die on the cross for the sins of the world, so as we trust Him, we are forgiven and have the hope of eternal life with Him. Not many Jews accepted Jesus as Savior, but the Gentiles were more receptive. About fifteen years after Jesus returned to heaven, Paul and Barnabas went on a mission trip to tell the Gentiles the good news about Jesus.
Acts 13: 46Then Paul and Barnabas spoke out boldly and declared, “It was necessary that we first preach the word of God to you Jews. But since you have rejected it and judged yourselves unworthy of eternal life, we will offer it to the Gentiles. 47 For the Lord gave us this command when he said, ‘I have made you a light to the Gentiles, to bring salvation to the farthest corners of the earth.’48 When the Gentiles heard this, they were very glad and thanked the Lord for his message; and all who were chosen for eternal life became believers.
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[1-5] Holy Bible, New Living Translation, copyright © 1996, 2004, 2015 by Tyndale House Foundation. Tyndale House Publishers, Inc., Carol Stream, Illinois 60188.