Having been set aside by the Holy Spirit for planting churches Paul and Barnabas set off to Seleucia and Cyprus, taking John Mark with them. Mark hadn't been specifically set aside by the Holy Spirit, but they clearly thought it was good to have a helper and it must have been amazing for him to go with them.
When they get to Paphos we get the first major encounter between the forces of light and darkness in this new ear of Spirit-led church planting. The proconsul was a bright man who was interested in the Word of God but seems very much in thrall to the false prophet and magician Bar-Jesus (=son of the salvation of Yahweh). v8 says that he deliberately tried to turn the proconsul from the faith.
Paul, full of the Holy Spirit, calls him for what he is: not "son of salvation of Yahweh" but "son of the devil, enemy of righteousness." And the judgment of God falls on the man in blindness. Following which the proconsul - probably the first genuine gentile convert with no previous background in Judaism - believes. Not because of the miracle but because he was astonished at the teaching (v12). Teaching attended by a sign.
How are we to apply passages like this? I can think of several options that I think are inadequate:
1. Only normalising the historical event. ie assuming God always has to do it like this. Teaching always has to be accompanied by signs and wonders
2. Only historicising the event. ie saying it was a one off and assuming God never does it like this any more. Teaching is never accompanied by signs, it is of purely historical interest. Praise God he did it that way then, but don't look for it now
3. Theologising it away. ie this is a sign miracle for the express purpose of the gospel going to a new field, in line with the overall structure of Acts. Or, that this was apostolic and therefore ceased withcompletion of the canon of scripture. Therefore we don't have to apply it to most or all of our situations today
I think it preferable to say that this is an example of Jesus being revealed to destroy the works of the evil one. This man sets himself up as a great power opposing God. Paul is granted the courage, insight and discernment to confront this spiritual force of wickedness and the gift of faith to know pronounce the miraculous judgment from God.
A retired missionary friend recently asked me if my generation has forgotten that Jesus was revealed to destroy the works of the devil. I think he is right. He said that in his view the forces of wickedness work differently in seular Britain to where he worked for many years in the East. There he saw demonisation and terrific fear of evil spirits. Possibly a bit like in Acts 13. Here, he maintained, Satan is much more likely to pose as an angel of light, espousing relativism, denying the existence of God (and Himself - read Screwtape!), and insisting that nobody invite anyone else to come to Christ or challenge other people's beliefs, under the guise of tolerant neutrality and niceness. My friend's contention was that this is pretty much the same thing as the evil demonisation.
Therefore I want to apply the underlying principle of Acts 13 to say that it is crucial for Christians, in the power of the Spirit, to confront evil. How do we recognise it? If it is trying to keep people from believing then it is evil. Its up to God whether he does confirming, judging miracles. But it is not up to us about whether we call evil for what it is.
We now live in a society that hates and persecutes people who call evil evil. It says we are intolerant and arrogant. There is huge pressure to shut up. All the power in society lies in the hands of those who would silence the gospel. But it did in Acts 13 as well. Let's pray for the powerful, palable sense of the presence of God to accompany evangelism. And let's remind ourselves that evangelism is far more than an exercise in logic, clarity of message or witnessing friendship. It is a spiritual activity opposed by spiritual forces of wickedness, whether that is evident demonisation or smilingly tolerant humnaists proclaiming the non-existence of God on the sides of London buses.