What does Acts 9:3 mean?

Saul is a young Jewish man, fiercely against Jesus and anyone who follows Him. He watched with approval when a mob killed Stephen. He persecuted the Jesus-followers in Jerusalem so violently they fled (Acts 7:58—8:3). As Christians spread through Judea, Samaria, and parts north, they taught other Jews how Jesus of Nazareth fulfilled the prophecies about the Messiah in the Jewish Scriptures. So many more have believed that Saul feels driven to follow and bring every Jesus-follower he can find back to Jerusalem for trial before the Sanhedrin, where he will either force them to deny Jesus or he will vote for their deaths (Acts 26:9–11).

This brings Saul to a road outside of Damascus, 133 miles north of Jerusalem, about noon (Acts 22:6). He has heard that Jesus-followers have infiltrated the synagogues there, and he wants to root them out. Suddenly, he's surrounded by a light from the sky: God's glory. He falls to the ground, and a voice asks him, "Saul, Saul, why are you persecuting me?" (Acts 9:4). His companions hear the voice and see the light but can neither see the speaker nor understand the words (Acts 9:7; 22:9).

Though not stated in this verse, Jesus apparently appears in the light. Ananias and Barnabas later affirm Jesus' appearance (Acts 9:17, 27), and Saul testifies to it (1 Corinthians 9:1; 15:8; Galatians 1:16).