A chariot on a desert road

Philip is having great success preaching in Samaria when an angel tells him to walk down a desert road. No reason given. On it he meets an Ethiopian official — the treasurer of a queen, a foreigner and a eunuch, which under the old law barred him from the temple assembly. He is reading Isaiah aloud in his chariot, the passage about a lamb led to the slaughter, and Philip asks if he understands it. How can I, unless someone guides me? Philip climbs up, starts from that Scripture, and tells him about Jesus. They pass water and the man asks what prevents him from being baptised. Nothing does. He goes on his way rejoicing, carrying the gospel to Africa before most of the apostles have left Jerusalem.