The eunuch was reading this passage of Scripture: 'He was led like a sheep to the slaughter, and as a lamb before the shearer is silent, so he did not open his mouth. In his humiliation he was deprived of justice. Who can speak of his descendants? For his life was taken from the earth.' The eunuch asked Philip, 'Tell me, please, who is the prophet talking about, himself or someone else?' Then Philip began with that very passage of Scripture and told him the good news about Jesus.
What an example we have here of how we are to share the gospel. The Ethiopian was reading from the scroll of Isaiah the prophet. You have to understand that, at this time, there was no "Bible" like we have today. Even having a piece of the Old Testament such as this would have been a big deal. The eunuch had the scripture and could read it but did not know that it was referring to Jesus.
Philip started with what the Ethiopian had and told him about Jesus. That is the same thing that we, as Christians, are called to do. The passage that the Ethiopian was reading is so powerful and describes Jesus' actions so well yet was written a long time before Jesus came to the earth. That, my friends, is what God can do!