Galatians 1:18-24

v18-21: Paul's knowledge of the gospel and his authority to preach it was not given to him by any other person.  His call to be an apostle and his qualifications for this role were "extraordinary and divine."  There is no reason to doubt that Paul was a genuine apostle and that the letters he wrote which have been preserved in Scripture are God's Word.

v22-24: When the Galatian Christians heard that this violent persecutor of Christians had been converted and was now preaching the gospel, they were filled with joy and glorified God, giving Him the praise and thanks for his wonderful saving work in Paul's life.  This is how we should respond whenever we hear reports of individuals or groups of individuals putting their faith in Jesus.