Why did Saul persecute followers of Jesus?
Saul persecuted followers of Jesus because he was thoroughly committed to Judaism, the Mosaic Law, and his Pharisaic identity. He regarded Jesus as an imposter destroying the bulwarks of Judaism, so he sought to stamp out the movement, believing he was doing God a favor through religious persecution.
Les explains that as Saul neared Damascus, a light from heaven suddenly shone around him, he fell to the earth, and he heard a voice saying, "Saul, Saul, why persecutest thou me?" Saul was totally religious, an absolute believer in the Old Testament, Judaism, and the Mosaic Law. He was a Pharisee of the Pharisees, of the tribe of Benjamin, a Jew through and through. Yet he hated Jesus of Nazareth with a passion because he felt Jesus was an imposter trying to destroy that which was his whole life. Saul believed Jesus was destroying the very bulwarks of Judaism, and he thought the only way to do God a favor was to overcome it and stamp it out with persecution. Les stresses that Saul was doing this in the name of religion, and warns not to lose sight of that.