Genesis 27:29 - Cursed be everyone who curses you, and blessed be those who bless you!
God said to Abraham, "I will bless those who bless you" (Genesis 12:3). That's God's position concerning the Jewish people then and now (Psalm 122:6). Why does praying for the city of Jerusalem bring prosperity? Because God promised the city of Jerusalem to King David and that His Seed, Jesus Christ, will sit on the Temple Mount and rule an eternal kingdom on earth.
Second, the blessing of God includes health and healing. Luke 7:1-10 is the story of the Gentile centurion who had a beloved servant who was dying. Because something practical was done to bless the nation of Israel, healing came to this man's home. It fulfills the Word of God.
Third, consider why God selected the house of Cornelius for the first outpouring of the Holy Spirit on the Gentile people in Acts 10:1-48. He did something practical to bless the Jewish people, and God poured out a supernatural blessing upon him.
Source: Life Lessons to Live By - Spiritual Benefits for Blessing the Jewish People