What does Acts 22:19 mean?

These verses are a bit complicated because they involve three different time periods.

The present is shortly after Paul returns to Jerusalem from his third missionary journey. Because of two different false accusations (Acts 21:20–21, 27–29), he finds himself defending his friendship with a Gentile to a murderous mob (Acts 21:30–31, 37–40).

During his defense, Paul talks about an event that happened decades before. While traveling to Damascus to hunt Jesus-followers, he met Jesus (Acts 9:3–19; 22:6–16). A several years later, he came back to Jerusalem (Acts 9:26–30). Upon his return, he went to the temple to pray. There, Jesus told him the Jews of the city would rather kill him than listen to his teaching about reconciliation with God through the Messiah (Acts 22:17–18).

Paul responded to Jesus by reminding Him of his past persecution of the church, including Stephen, the first martyr (Acts 7:54–60; 22:20). Paul seemed to think that his former violence validated his message of God's forgiveness. Jesus told him it didn't, but it did open an opportunity for Paul to present that message to Gentiles (Acts 22:21).

Back to the present: when Paul mentions his mission to Gentiles, the mob remembers that they're angry. They call for Paul's arrest, and the Roman tribune takes him away (Acts 22:22–24).