Called by God - Galatians 1:10-24

Following on the twice repeated “accursed” of verses 8&9 Paul conveys the reason for the corrupting of the gospel - seeking to please man rather than serve God.

Even though Paul was in rebellion against God, violently persecuting the Church, he was still of the elect and God turned the evil that Paul was engaged in to good for the cause of the gospel.

Paul’s past was horrific to consider. He was an outright enemy of the Lord, persecuting and sending believers to their deaths. But Christ transformed him mightily, made him a new creation, and set him on the path of service in the cause of the gospel.
I am sure Satan used Paul’s past against him, throwing it up before him to instill feelings of guilt and remorse. Satan is an accuser, and Paul’s past gave him much to use against him.