There really is not a break between verse one of this chapter and the last verse. Paul is continuing with his explanation of the “sonship” and “heirship” of the believer. Whoever divided up the chapters of this book really did not know what he was doing.
1. In verses 1-7 of this chapter Paul explains the two stages of any son:
a. At first he is no better than any servant (slave)–verses. 1-3
b. Then he comes of age–verses. 4-7
2. In verses 8-11 Paul describes the freedom of the believer.
a. First he describes the Galatian believers former enslavement as sinners–verse 8
b. Next he describes the Galatian believers knowledge of God as believers–verse 9.
c. Then he describes the Galatian believer’s observance of Jewish legalism (verses 10-11).
3. In verses 12-20 we see the strain between Paul and the Galatian believers.
a. First Paul expresses their past warmth–vv. 12-15.
b. Then Paul expresses their present coldness–vv. 16-20.
(1) The Judaizers had changed their attitudes toward Paul (verse 16).
(2) They seemed to like what the Judaizers were teaching–(verses 17-18)
(3) Paul expresses his desire to be with the Galatian believers–(verses 19-20)
4. In verses 21-31 Paul explains the conflict between Issac and Ishmael.
a. Hagar stands fors the Old Covenant of the Law, made on Mt. Sinai.
b. Sarah stands for the New Covenant in Christ Jesus; God’s new way of dealing with sin–the Child of Promise.