Adam Clarke on Galatians 1:7

Which is not another - It is called a gospel, but it differs most essentially from the authentic narratives published by the evangelists. It is not gospel, i.e. good tidings, for it loads you again with the burdens from which the genuine Gospel has disencumbered you. Instead of giving you peace, it troubles you; instead of being a useful supplement to the Gospel of Christ, it perverts that Gospel. You have gained nothing but loss and damage by the change.