The apostle Paul wrote that “For the preaching of the cross is to them that perish foolishness; but unto us which are saved it is the power of God.” (1 Corinthians 1:18). So why preach the gospel when the perishing people around us believe it to be foolishness? Paul answers that question in the statement: “Unto us who are saved it is the power of God”.
Philip was chosen by the Church to be a servant to the Church to serve the Grecian widows (Acts 6), and he went about preaching the Gospel of Christ with many believing.
We can believe that Philip always preached Jesus Christ through the Scriptures. We must remember that the only Scriptures Philip had, and the only Scripture the others had was the Old Testament; and they preached Jesus from there.
The Purpose of the Scriptures is to reveal to us Jesus. The Purpose of Preaching is to expose Jesus in the Biblical text; and that is what Philip did with the Ethiopian eunuch. That is what the preacher today is called to do. In showing the greatness, power , and glory of God and His Son; we also expose the sinfulness of humankind, and our need for Him.