Answer:
According to Acts 9:1-2
"In Jerusalem Saul was still trying to scare the followers of the Lord, even saying he would kill them. He went to the high priest and asked him to write letters to the synagogues in the city of Damascus. Saul wanted the high priest to give him the authority to find people in Damascus who were followers of the Way. If he found any believers there, men or women, he would arrest them and bring them back to Jerusalem. "
And you know the rest of the story, Jesus appears to him and blinds him. If you need more context go to Acts 9.