The mission team reach the cities of Lystra and Derbe. These towns are Gentile and pagan, not Jewish. All we know about the gospel work in Derbe was that the good news was preached and a lot of disciples won for the Lord. But in Lystra things went very differently and very nastily.
I think we are meant to note the contrast. The message preached was the same in both places, and the method was probably similar too. Why did things go well in one place and not the other? Did Paul and Barnabas just do a bad job in Lystra? I have been in university mission meetings that were fruitful one day and incredibibly difficult and frustrating in another town the next. The temptation is to think "if we teach the message right then all goes well; if things go badly it must be because we got something wrong." Lystra and Derbe show the deficiency of that view. The same message divides people according to how they hear. The real gospel, truly preached, produces both openness and hostility.
The approach in Lystra is totally different to that in Jewish Pisidian Antioch. They don't preach in the synagogue. In fact they don't mention the Old Testament scriptures at all - a sermon without using the Bible! The incident starts not with an exposition but with a sign miracle, specifically a healing (in which we are clearly meant to hear echoes of Acts 3). I find it interesting that God does a sign miracle that the people dramatically misunderstand. Did God not know that they would get it wrong and mistake Paul and Barnabas for Hermes and Zeus? Yes he did. So why did he do the miracle? That is the chief question I want to put to this passage: why the miracle? We assume it isn't random. We assume that Luke tells us this strange incident for a reason.
What the miracle does is expose the heart and worldview of the people. It reveals the underlying spiritual dynamic with which the gospel has to compete: idolatry. In Pisidian Antioch the hurdle that needed to be overcome was that the people had to realise that they could now be justified by Jesus from everything that they couldn't be justified from by the Law of Moses. That was the sticking point, the point where the gospel challenged everything for them. in Lystra the hurdle that needed to be overcome was that they worshipped idols. That is the point the gospel challenges pagans - to give up what they worship. Most of the time when I talk to non-Christians today I have in my mind that I am talking to idol-worshippers. It's often no good trying to reason with them firstly from the scriptures like in Pisidian Antioch. We need to listen to what Paul and Barnabas did in Lystra instead, arguing for the good news and for God's existence, goodness, creative acts and kindness from the world around them.
The crux of the chapter is in v27: back in Antioch they explained how God opened the door of faith to the Gentiles. He opened it through them going to supersititious pagans who loved them one minute and turned nasty the next, through Paul being stoned and thought dead, and through preaching to people who didn't respond as well as to those who did.
They needed to have been filled with and commissioned by the Holy Spirit. Who would have been equal to this otherwise? But this is what the Spirit did with those he filled and commissioned. It's glorious, but extremely difficult. The message of grace spread powerfully but through extreme discomfort. If we sit in churches praying to be filled with the Spirit but with absolutely no intention that we should sacrifice our comfort for spreading the gospel, it shouldn't surprise us if the Holy Spirit declines to bless our indolence.