What does Acts 9:9 mean?

Saul, the persecutor of the church (Acts 8:1–3), has met Jesus on the road to Damascus (Acts 9:1–8). Jesus has confronted him with his violence toward His followers, and Saul has become blind because of the great light of heaven. He is now in the house of a man named Judas in Damascus, on Straight Street (Acts 9:11), awaiting further instruction from Jesus. Possibly to clear himself of distractions, he fasts for three days. This was the typical length of time traditionally used to repent or wait for God's Word.

Undoubtedly, through this time, Saul is thinking over and repenting of his actions. He watched over the coats of the mob while they stoned Stephen (Acts 7:58). He dragged people from their homes and took them to prison (Acts 8:3). He ran people out of town. He tried to make them deny that Jesus is the Son of God, or to say something which he could use to convict them of death (Acts 26:11). He cast his vote for execution when they were convicted (Acts 26:10). And he did it all "in raging fury" (Acts 26:11).

Ananias, the follower Jesus has chosen to lead Saul to faith, is reluctant to meet the man who had come to arrest the Jewish Christians. Jesus tells him, "Go, for he is a chosen instrument of mine to carry my name before the Gentiles and kings and the children of Israel. For I will show him how much he must suffer for the sake of my name" (Acts 9:15–16). Saul's experiences on the mission field do somewhat mirror what he did to others. He is stoned in Lystra, although he miraculously survives (Acts 14:19–20). He is beaten and imprisoned (Acts 16:22–24). He is run out of town on numerous occasions, including from Damascus (Acts 9:23–25) and Jerusalem (Acts 9:29–30). He is accused of blasphemy (Acts 24:6). He is nearly assassinated by the Jewish council (Acts 23:12–15). Enraged Jews from Thessalonica not only form a mob in their city but, when they find out that Saul/Paul is preaching in a nearby town, they even travel to Berea to agitate crowds against him there (Acts 17:5, 13). Paul gives a list of many of the sufferings he endured in spreading the gospel in 2 Corinthians 11:23—12:10.

In these three days, Saul will likely contemplate his flawed perspective against God. He seems to quickly notice where he was wrong in his doctrine, and the message he should be preaching (Acts 9:20). However, he almost certainly does not yet suspect how he will fill "up what is lacking in Christ's afflictions for the sake of his body, that is, the church" (Colossians 1:24; Acts 9:16). For now, while he sits blind, he sees that he has been horribly wrong and that he needs forgiveness from God the Father and the Son. When Ananias comes to offer that forgiveness, Saul takes it. All the passion he used to destroy Jesus' followers will now be used to multiply them.