…. the story of Philip and the Ethiopian eunuch teaches us one of the ways God uses to evangelize the world. I say “one of the ways God uses” because it is clear from the book of Acts that a lot of evangelism was done without an angel of the Lord having to tell the Christians to do it (e.g., 8:4). It’s what one does if one loves Jesus and loves people. You tell the good news. Jesus already gave us a command to be about it in the Great Commission. So you don’t have to have an angel of the Lord to tell you to do it any more than you need an angel of the Lord to tell you not to do it.
But on the other hand, we may be more in danger of making the other mistake, namely, of thinking that we can do all God wants done by simply evangelizing according to our own planning. So God includes in his inspired Word stories and teachings that equip us for another kind of good work—not just wise and prayerful planning on the basis of circumstances we can see, but also listening responsively to the Spirit when he may want to tell us to do something that we might never think of doing through our own planning—like, “Go down to a desert road that leads to Gaza and wait for further instructions.” Philip could not have computed form Scripture and circumstances that that’s where the Spirit was moving next.
So the Scriptures are wonderfully sufficient here—they protect us from the error of thinking that the only way God guides us in good work is by reasoning and planning from circumstances and principles (though this is good), and they show us that there are works God may lead us to do by means of extraordinary guidance. I count at least 18 instances of this extraordinary guidance in the book of Acts scattered among all the more ordinary ways of making decisions in evangelistic strategy. And since there is no teaching anywhere in the New Testament that says this work of the Lord is limited to the time of the book of Acts, we should assume that one of God’s ways today of building his church is to give direction to his people in extraordinary ways as well as more ordinary ones.