What does Acts 16:17 mean?
Paul, Silas, Timothy, and Luke are in the city of Philippi on the border of Macedonia and Greece. They have found a small group of women who meet at the riverside to pray to the Jewish God, although it's likely at least some of them are Gentiles. Some people in town own a demon-possessed slave girl who tells fortunes. The demon in the girl has recognized that Paul's team serves Jesus (Acts 16:13–16).This is not the first demon who has publicly identified God's servant; Jesus had to deal with this several times. Demons called Him "the Holy One of God" (Mark 1:24–25) and the "Son of God" (Mark 3:11–12). In each case, Jesus silenced the demon (Mark 1:34). On the surface, one supernatural being validating the message of the servants of another supernatural Being may seem like a good thing. However, since the beginning, Satan has excelled at adding a little lie to a big truth with catastrophic effect. Christ did not need or want validation from lying spirits bent on destroying everything good in the world. He was also not ready to publicly reveal Himself as the Messiah and the Son of God, so He forbade them to speak and expelled them from their victims.
Paul's actions are decidedly more human. He expels the demon, but because it's annoying, not necessarily dangerous (Acts 16:18). Some commentors suggest the girl's words are sarcastic or taunting. It's also possible she is simply following the missionaries closely and being loud and disruptive.
Another question is, why does the demon speak at all? Why does it accurately declare that Paul and Silas are teaching the way to salvation? In Jesus' ministry, demons seemed to be compelled to approach Him. There's no record in the Gospels that indicates they lied in His presence. This demon does the same. There is something about the power of God in these situations that overrides the demons' natural inclination to lie and hide and forces them to reveal themselves. As the apostle John writes, "The light shines in the darkness, and the darkness has not overcome it" (John 1:5).