On his first missionary journey, Paul the apostle preached the gospel to Jews living in Antioch of Pisidia. He correctly assumed that they were familiar with the promises God earlier made to King David, that one of his descendants would sit upon the throne of Israel forever. (2 Samuel 7:12-13)

“And it is one of King David’s descendants, Jesus, who is God’s promised Savior of Israel! 24  Before he came, John the Baptist preached that all the people of Israel needed to repent of their sins and turn to God and be baptized. 25  As John was finishing his ministry he asked, ‘Do you think I am the Messiah? No, I am not! But he is coming soon—and I’m not even worthy to be his slave and untie the sandals on his feet.’ Acts 13:23-25 (NLT)  

When we share the gospel with those who are not as familiar with the Bible, we have an opportunity to explain how Jesus came in fulfillment of promises made to Israel long ago.

The gospel only makes sense when we understand its historical context. God promised that one day a Savior would defeat Satan and deliver us from his dominion. This began in the Garden of Eden, continued with Abraham, Isaac, and Jacob, was reiterated to Moses, amplified with King David, and prophesied by Isaiah and others.

What was not understood until God revealed it to Paul was that the Messiah was sent to save the entire world, not just Israel.

He says, “It is too small a thing that You should be My Servant To raise up the tribes of Jacob and to restore the preserved ones of Israel; I will also make You a light of the nations So that My salvation may reach to the end of the earth.” Isaiah 49:6 (NASB95)
For God so loved the world, that He gave His only begotten Son, that whoever believes in Him shall not perish, but have eternal life. John 3:16 (NASB95)

By referring to this, when you read you can understand my insight into the mystery of Christ, 5 which in other generations was not made known to the sons of men, as it has now been revealed to His holy apostles and prophets in the Spirit; 6 to be specific, that the Gentiles are fellow heirs and fellow members of the body, and fellow partakers of the promise in Christ Jesus through the gospel, Ephesians 3:4–6 (NASB95)

One day in the not so distant future, the very real historical person named Jesus, the glorious resurrected Son of Man prophesied by Daniel, will return in the clouds with great power to judge all mankind.

At that point in time, all the earth will come to realize that the gospel is a wonderful announcement of mercy to those who believe it which is based on the historical facts relating to Jesus’ life, death, and resurrection. It is also a narrative of the historical fulfillment of God’s promises to Israel.

Therefore, it is important for gospel preachers to familiarize themselves with the the Old Testament and how it points to Jesus and the glorious gospel that is offered to every person in the world, regardless of ethnicity, gender, age, or socioeconomic status. That is how the early church presented Christ, and so should we!

If you are inclined to learn better how to do this, I suggest Scot McKnight's masterpiece, The King Jesus Gospel. I wrote a summary, which you can access by clicking here.