Philip runs to the chariot (ESV: ran, “pros-trecho,” see also Matthew 27:48; Matthew 28:8; and John 20:2, John 20:4) and ends up walking next to the chariot. The man is reading aloud words from Isaiah 53:1–12. Reading the Bible aloud was normal in those days. Philip hears quite clearly that the foreigner reads from Isaiah in the Greek language.
What a unique opportunity God gives to Philip! The Ethiopian is already reading Scripture about Jesus. See how God is already busy with this Ethiopian and prepares everything for Philip, so that he can talk to the man about Jesus Christ! God is continuously one step ahead of him.
30 So Philip ran to him and heard him reading Isaiah the prophet and asked, “Do you understand what you are reading?”