Paul had been killing Christians. When he did this he persecuted Jesus. One day when he was headed to Damascus Jesus himself confronted Him. From that day on, Jesus began ruling His life.

Acts 9:

9 Meanwhile, Saul was uttering threats with every breath and was eager to kill the Lord’s followers. So he went to the high priest. 2 He requested letters addressed to the synagogues in Damascus, asking for their cooperation in the arrest of any followers of the Way he found there. He wanted to bring them—both men and women—back to Jerusalem in chains.

3 As he was approaching Damascus on this mission, a light from heaven suddenly shone down around him. 4 He fell to the ground and heard a voice saying to him, “Saul! Saul! Why are you persecuting me?”

5 “Who are you, lord?” Saul asked.

And the voice replied, “I am Jesus, the one you are persecuting! 6 Now get up and go into the city, and you will be told what you must do.”