In the beginning of most of his epistles Paul definitely declares his apostleship. In this instance, in a parenthesis, he defends that declaration more emphatically than in any other introduction. The absence of personal salutations is marked. He does not, however, omit the salutation of the Gospel. Grace and peace are for them also.
As there are no words of personal salutation, so also there are no expressions of thankfulness for the Galatians' condition. Instead of the usual, "I thank my God," we find him writing, "I marvel." These people were "so quickly," that is, so easily "removing" from the Gospel. There were those who troubled them. These troublers were perverting "the Gospel of Christ." They were insisting on fleshly ceremonies (3:1, 3), on the observance of days (4:10), on circumcision (5:2), and on a new legalism (5:4). This was utterly subversive of the evangel of the Cross. The apostle showed the completeness of the Gospel by telling his own story.
The divine element throughout is clearly marked. There was, first, the revelation to him of Jesus Christ, then the revelation in him of the Son of God, and, finally, such revelation through him that the churches of Judea, though they did not know his face, glorified God in him.
the Week of Proper 20 / Ordinary 25