What does Acts 9:18 mean?

Sight has been used as a metaphor for understanding worldwide throughout history. In Scripture, it's particularly used, as in Isaiah 6:9–10, with those who should know better. Stubborn people often have all the information about God that they need, but they refuse to act on it. Saul fits this description. He was "educated at the feet of Gamaliel according to the strict manner of the law" (Acts 22:3). His zeal for the Mosaic law was such that he unquestioningly hunted down Jesus-followers to either return them to orthodox Judaism or see them executed (Acts 26:9–11). His violence and rage against God's people seem to make him a perfect candidate for God to harden his heart and leave him to his hate.

But Jesus claims him (Philippians 3:12). After a period of physical blindness (Acts 9:9), Jesus removes the scales from Saul's eyes and heart. Saul knows his sinful character, calling himself the least of the apostles (1 Corinthians 15:9; Ephesians 3:8), but by the grace of Christ, he is redeemed (Romans 7:24–25) Now, he is called to bring spiritual sight to the Gentiles.

It is customary at the time for a new convert to be baptized immediately (Acts 2:41; 8:12, 36–38; 10:47–48; 16:15, 33; 19:5). It was the cultural signifier that someone had left their previous religion or sect and joined another. Later, Saul will testify that Ananias also told him his mission to bear witness to what is happening to him (Acts 22:15). At another time, Saul says that Jesus gave him the mission to preach, particularly to the Gentiles (Acts 26:16–18). That Ananias reaffirmed Jesus' message would provide greater validation for both.