Sermons on Galatians 1
The freest people in the world are those who submit most fully to the authority of Christ in Scripture.
There is one, and only one, gospel. It is therefore astonishing--and tragic--to turn away from it and lose both God and his grace.
To try to explain the change from Paul's pre-conversion persecution to his post-conversion passion for the gospel merely by the work of men is to grasp at a straw.