I have had my own experiences of being out in the middle of nowhere half way around the world and having someone approach me out of the blue to either make a confession of faith in Christ or to ask why I was there. Luke’s account of Philip’s encounter with the Ethiopian tells us that these encounters are not chance but divinely inspired. Jesus had said that repentance and faith would be preached throughout the world beginning in Jerusalem and Luke is telling his benefactor Theophilus that it is happening. In those days Ethiopia was considered to be the end of the earth. Homer mentions in the Odyssey Ethiopians lived on the Southern edge of the earth.
As the IVP Bible commentary puts it –
God is actively fulfilling his purposes for the scope of the church’s mission (Lk 24:47; Acts 1:8). If it reaches an Ethiopian so soon after its beginning, Theophilus can know for sure that the gospel that is to be preached among all the nations is true. It is for him, and for us too.