Now this is an allegory. Gal. 4:24
The Jewish teacher Paul is arguing against presumably believes himself to be a good and faithful follower of Jesus and simply wants the other members of the congregation (and particularly the Gentiles) to obey the rules laid down in Scripture (as the teacher interprets and applies them).
Under the New Persepctive, the question Paul answers is not “What must I do to be saved?” but “How do the life, death, and resurrection of Jesus fit into God’s continuing faithfulness to the promises he made to Abraham to bless all people and all creation through his seed (Gen 12:3)?”