1 Paul, an apostle—sent not with a human commission nor by human authority, but by Jesus Christ and God the Father, who raised him from the dead— 2 and all the brothers and sisters with me,
To the churches in Galatia:
3 Grace and peace to you from God our Father and the Lord Jesus Christ, 4 who gave himself for our sins to rescue us from the present evil age, according to the will of our God and Father, 5 to whom be glory for ever and ever. Amen. (TNIV)
For those who are familiar with Paul's letters one of the most striking elements of Galatians is the absence of an introductory thanksgiving. Typically Paul thanks God for the addressees of his letters right after the salutation (e.g., Phil. 1:3-11, Rom. 1:8-10). Not so in this case. Here in Galatians, Paul does not have a single word of praise for the Galatians. This shows that the situation there was really bad. He is so upset with their abandonment of the gospel that he has nothing good to say about them.
As Dunn points out, this becomes even more forceful when you consider what Paul replaces the thanksgiving with: a thanksgiving for the work of redemption effected through Jesus Christ (vs. 4). Most scholars consider verse 4 to be a snippet of an early church creed or confession (see esp. Longenecker), making Paul's stinging rebuke even more forceful. They are so far off, that rather than thanking God for signs of grace in their lives he must give them a stinging rebuke by reminding them of the basic confession of their faith. They apparently had lost sight of the fact that it was Christ alone who was the means of reconciliation with God and thus the sole grounds of membership in the people of God, and as we see here and will see in the next section (and throughout the letter), Paul has nothing but the harshest criticism for them.