Galatians 3:8 is a quotation of Genesis 18:18, by which Paul argues that the blessing of Abraham was always meant to extend to the Gentiles through Abraham’s faith in God (cf. Gen 15:6). Abraham, however, did not see God’s blessing extended to the Gentiles in his day, as can be seen in Gen 18:20-33. Paul quotes Gen 18:18 to illustrate that God’s promise of blessing the nations was now fulfilled through the gospel going to the Gentiles.
I will argue for Paul’s quotation of Gen 18:18 over against Gen 12:3 or 22:18, utilizing Jeannine Brown’s methodology for “storied metalepsis,” which analyzes the storied elements (setting, plot, and characters) of the text in reference. The quotation of Gen 18:18 refers to the surrounding story, namely, that God will bless the nations through Abraham’s lineage despite Abraham not yet seeing the nations of Sodom and Gomorrah blessed with righteousness (Gen 18:16-33). Galatians 3:6-18 argues that righteousness has now reached the nations by Abrahamic faith in the offspring of Abraham. In other words, God’s promise had been kept through Christ. This interpretation impacts the reader’s understanding of righteousness, Abraham, and blessing in Galatians. Reading Gal 3:8 as a metaleptic quotation of Gen 18:18 is the best path forward for understanding Paul’s argument in Gal 3.