Why did Paul reprove the people in his letters?
They were reproved because they had lost sight of what God had instructed, having been blinded by a lack of faith. They were leaving Paul's doctrine of faith plus nothing and returning to legalism because their faith had grown weak.
Les explains that every one of Paul's writings came up through doctrine, reproof, and correction, all based on Paul's premise of faith plus nothing. The people were reproved because they had lost sight of what God had instructed and were blinded by a lack of faith. They were leaving Paul's doctrine of faith plus nothing and going back into legalism because their faith grew weak. This same pattern appears in the Ephesian letters, where comprehending that we are seated in the heavenlies is by faith, not by feeling.