What does Acts 9:21 mean?
Saul, the passionate Pharisee, has recently converted to follow Jesus (Acts 9:1–19). The first thing he does is start preaching. He goes to the synagogues in Damascus and shows how Jesus of Nazareth fulfills the prophecies of the Messiah in the Jewish Scriptures.He had originally come to Damascus to arrest Jesus-followers, bring them to Jerusalem for trial, and, if they didn't deny their faith, see them executed for blasphemy (Acts 26:9–11). Apparently, this news is well known among the Jews there. Now, Saul is preaching that Jesus is the Messiah and the Son of God; when Jesus made this claim, the Sanhedrin had Him crucified for blasphemy (John 19:7).
The phrase alternately translated "made havoc," "was ravaging," or "destroyed" is from the Greek root word portheō. In general, it means to wreck or overthrow, and is based on the Greek pertho which means "to sack." Believers of this era saw Saul as an invading warrior who had come to demolish the church.
"This name" is the name of Jesus. This is not a reference to the letters and sounds that identify Him, but to the entirety of how He is known. It means Christ's character and reputation, the thoughts and feelings that come to mind when people consider Him. Syllables and sounds are ephemeral. We put our hope and faith in the person of Christ.