The Ethiopian takes the initiative and commands the driver to stop the chariot. They both get out and then Philip baptizes the Ethiopian. To baptize (“baptizein”) is more often found in Acts (e.g., Acts 2:41; Acts 8:12; Acts 9:18; Acts 10:47; Acts 16:15).
The story is told beautifully. They both get out, step into the water, and come out again. Through this baptism, the Ethiopian belongs to Jesus Christ, and he is engrafted in his church. This baptism does not create any problems later on in the young Christian church in Jerusalem, as did the baptism of Cornelius by Peter (Acts 11:1–18), perhaps because the Roman Cornelius was much closer and perhaps known to them?
38 And he commanded the chariot to stop, and they both went down into the water, Philip and the eunuch, and he baptized him.