What does Acts 21:9 mean?

We know Paul, Luke, and several men from the churches Paul planted (Acts 20:4) are headed to Jerusalem. The men are bringing donations to the Jerusalem church from their own congregations in modern-day Turkey and Macedonia (Romans 15:26). Paul is compelled by the Holy Spirit to go to Jerusalem where he knows he will be imprisoned (Acts 20:22–24). Along their way, they stop in Caesarea.. It seems reasonable to think Philip's daughters do tell the rest of the church that Paul will be arrested. In the next breath, Luke says Agabus, the famous prophet from Acts 11:28–30, arrives and foretells the same thing.

The church in Caesarea, like Paul's companions, misunderstand the prophecy. The Holy Spirit is not directing them to rescue Paul from hardship. God is giving them the opportunity to encourage Paul as he prepares to face hardship.

The Bible makes no qualms about women prophets. Huldah validated the Law for King Josiah and prophesied God's judgment against rebellious Judah (2 Kings 22:14–20). Anna met the baby Jesus (Luke 2:36–38). Paul gave instructions to women prophetesses in 1 Corinthians 11:5. There are biblical debates about whether prophets still exist and the difference between speaking conviction versus forecasting the future. However, there is no question that at times, God chose women to be prophets.