"Then Saul, still breathing threats and murder against the disciples of the Lord, went to the high priest and asked letters from him to the synagogues of Damascus, so that if he found any who were of the Way, whether men or women, he might bring them bound to Jerusalem. As he journeyed he came near Damascus, and suddenly a light shone around him from heaven. Then he fell to the ground, and heard a voice saying to him, 'Saul, Saul, why are you persecuting Me?' And he said, 'Who are You, Lord?' Then the Lord said, 'I am Jesus, whom you are persecuting. It is hard for you to kick against the goads.' So he, trembling and astonished, said, 'Lord, what do You want me to do?' Then the Lord said to him, 'Arise and go into the city, and you will be told what you must do'" (Acts 9:1-6).
Saul of Tarsus escalated his persecution of the church far beyond the city limits of Jerusalem. It could be that he had expected the movement to die after it was essentially crushed in Jerusalem, but news must have filtered back that the scattered disciples were building up congregations elsewhere. Saul was determined to destroy the church and this challenge only further motivated him. He received written authority from the high priest to arrest any Christians he found in Damascus (a city with a large population of Jews located over 130 miles northeast of the temple) and bring them back to Jerusalem. He was on a "missionary journey" of destruction, you might say. The gender of those following Christ was insignificant to Saul. He breathed "threats and murder" against all those who followed "the Way"! The singularity of "the Way" is important to note (cf. John 14:6). Early Christians were united in their course of life.
As he approached Damascus, Saul was surrounded by a bright light from heaven, which caused him to fall down. Jesus Christ spoke to him from heaven - "Saul, Saul, why are you persecuting Me?" Here we learn, perhaps for the first time, of the inseparable link between Jesus and His spiritual body (the church). Although Saul was only intending to persecute Christians, he was actually persecuting Jesus Himself! Such is not difficult to understand since the church is the body of Christ (and is made of up all Christians) and He is its head (cf. Eph. 1:22,23; 5:30). To persecute the body is to persecute the head, since both are intimately connected (cf. Luke 10:16). Let those who claim to only want Christ but not the church, consider this truth carefully.
Saul is shaken and asked who was speaking to him. He was evidently uncertain until hearing the Lord declare - "I am Jesus, whom you are persecuting. It is hard for you to kick against the goads." Jesus explicitly identified Himself to Saul. Now it was up to Saul to either believe or continue rejecting the truth. Thankfully, we will see him making the right and wise choice shortly! What did Jesus mean by stating that it was hard for Saul to "kick against the goads"? I believe the thought is that Saul had been having more and more difficulty resisting the truth the Christians had been declaring. Although it would be going too far to say that Saul was violating his conscience by aggressively hunting Christians, it is accurate to say that his conscience was being pricked or bothered at times, due to his behavior. Saul is an example of a man with a good and honest heart. He zealously wanted to do what was right, and, even before this conversation with the Lord, he struggled with his current volatile course to some degree.
Jesus' declaration penetrated Saul to his core. I doubt any today can really fathom the force of emotion which must have ripped through Saul's soul when Jesus identified Himself. Previously, Saul viewed Jesus as an imposter and His followers as blasphemers worthy of death, but he was wrong and is now both fearful and amazed, realizing the terrible course he had charted against them. He felt his guilt and would throw himself upon the Lord's mercy. Here is where we first see Saul as a penitent believer - "Lord, what do you want me to do?"
The Lord instructed him to continue on to Damascus where he would be told what he "must do." It should be observed that Jesus did not tell him everything he needed to do in order to be saved. In fact, it will become increasingly clear that at this juncture Saul is not yet saved (such a point cannot be overstated). God would arrange for a Christian to teach Saul the gospel, so he could obey it (that was one of the things Saul must do). This is a recurring pattern in Acts. Neither angels nor deity tell a lost soul what they must do to be saved, but they do bring together both saved and sinner so the latter can be taught by the former.