In this chapter, Philip's preaching in Samaria has been going strongly, but in the middle of it he's told by God to go south -- a little like Abraham in Genesis 12, but here, toward a place and with no direction about why. When he gets there, the Holy Spirit tells him to get close to the vehicle he sees on the road. The man riding in it is returning from worshiping God in Jerusalem, and reading about a strange character in Isaiah. Philip offers to help him understand.
The Ethiopian, being a gentile, has been Jerusalem to worship, but has not been allowed into fellowship at the temple. Not only is he not Jewish, he's physically incomplete, so even if he were Jewish he would still be on the outside, straining to see the pageantry of the sacrifices and hear the music and the blessings of the priests. Philip, on the other hand, is happy to spend time with him. He explains that the suffering servant this man is reading about is the true Messiah he has heard about from the Jews, who through his life and death and resurrection has opened the gates for everyone to come into the house of God. The Ethiopian asks if he can be baptized. In this context, it's a loaded question -- he wasn't made welcome in the Jewish religion, so can he be welcome in this new one?
For answer, Philip leads the Ethiopian down into the water. They walk together -- the text in verse 38 is a little repetitive, just so we get the point that Philip was his companion on the journey to inclusion. Baptism is the sign of entry into this new covenant with Jesus, and this stranger becomes a member of the family through Philip's ministry. And once more, heaven has a party (Luke 15:7, 10).
In this story is one major theme: the new society Jesus founded is not a closed society, but welcoming to all. That's not how we humans think -- but Jesus does. He showed that by spending much of his time with 'outsiders' including sinners and non-Jews, and continued his ministry through Philip to this man.
So for you, right now, who is your Ethiopian? Who is your eunuch? Who would you have a hard time welcoming? What kind of people do you not feel comfortable with? Is there anybody to whom you would not offer a warm welcome and your friendship? Who is it you are not sure "belongs"? Is it someone from another race? An immigrant who doesn't speak any English and you suspect may not be here legally? Someone who is LGBT? Someone with a disability or disfigurement?
Whoever it is, Jesus says he or she belongs too. Jesus continues his ministry through the Holy Spirit in people, as we read above, to bring all people to himself. Whoever they are right now, he makes them children of God as they respond (John 1:12), and includes them in this new society of his church.
You'll probably meet one of those people today or tomorrow. Will you be more like the Jews, or more like Jesus and Philip? Let the Holy Spirit direct you to join Jesus in his ministry of inclusion.