What does Acts 16:16 mean?

The Holy Spirit has called Paul, Silas, Timothy, and Luke to Macedonia to spread Jesus' offer of salvation. When they arrive in Philippi, they find there are not enough Jews in the city to have a synagogue. Knowing the custom, they presume they will find a group who worship the Jewish God at the river. They do—a gathering of women including Lydia who accepts their message of Jesus and invites them to stay with her (Acts 16:9–15). Apparently, the group continues meeting at the river, listening to Paul and Silas talk about Jesus.

In most cities, Paul would speak in the synagogue, showing how Jesus fulfilled the prophecies of the Messiah in Jewish Scripture. After a while, the synagogue leaders would reject his message, but others—Jew and Gentile—would follow him and learn more. Eventually, the synagogue leaders would incite the city leaders to drive Paul out of town, at least once by stoning him (Acts 14:19–20). In Philippi, Paul learns that threatening a Gentile's money stream can be as dangerous as challenging a synagogue's teaching.

The "spirit of divination" that possesses the girl is related to the myth of Pythian: a serpent or dragon that guarded the oracle at Delphi and had been slain by Apollo. The girl is possessed by a demon that has taken on this myth—but this does not validate the existence of the "spirit of python." Some churches teach that every hardship and sin, from unemployment to poor health, promiscuity, and even stubbornness is caused by a demon. Many teach that the "python spirit" can thwart a Christian's communication with the Holy Spirit, both blocking the Spirit's leading and the believer's prayers. Others say Python squeezes away their joy or causes greed or fear.

These are false teachings. Not every hardship is caused by a demon; the world is fallen, and bad things happen when people make wrong choices. A demon can oppress a Christian, but it cannot possess someone who is indwelt by the Holy Spirit. Demons have been around for a long time, and they can use that experience and their ability to observe those around us to reveal things a normal person doesn't know, but there's no indication they can determine the future.