What does Galatians 1:13 mean?

Paul has stated that anyone who attempts to preach a different gospel is, in fact, preaching something entirely false and is worthy of being cursed (Galatian 1:8–9). And yet, a group known as the Judaizers has been attempting to persuade Christians in Galatia that Paul was not trustworthy. Paul has stated unequivocally that he learned what he taught to them directly from Jesus Himself.

To make that case, Paul now begins to remind his readers of his own personal story. After all, he was once one of the most prominent persecutors of Christians. His goal was nothing less than to destroy the "church of God" by any means necessary, including violence. According to Acts 26:9, he "was convinced that [he] ought to do many things in opposing the name of Jesus of Nazareth." This included imprisoning believers, casting his vote to have them executed, and chasing them down even to cities outside of Israel.

Most famously, Paul's first appearance in the Bible is at the stoning of Stephen (Acts 8:1–3).