A. Andrew Das, “Israel’s Scriptures in Galatians,” in Israel’s Scriptures in Early Christian Writings: The Use of the Old Testament in the New, edited by Matthias Henze and David Lincicum (Wm. B. Eerdmans Publishing Co., 2023), 395-396.
Galatians 3:16 quotes exactly what the Scripture “says” (λέγει) in Gen 13:15 LXX as Paul returns to the topic of the plural “sons” of Abraham raised in Gal 3:6-7. He clarifies, however, that the words “and to your seed” refer to a single individual. The notion that the “seed/offspring” promised to Abraham is grammatically singular would have surprised Paul’s contemporaries. Genesis 13:16 employs the word “seed/offspring” for Abraham’s collective descendants. Paul denies the collective sense of the word. As justification for his interpretation, Paul could well have pointed to Isaac as Abraham’s single son of promise (Gen 22:2, 12, 16-17; 24:7; cf. Jubilee. 16:17-18: Jacob as the single seed of Isaac but then his descendants as a collective seed – an interplay). Genesis 22 stresses in three separate instances that Isaac was Abraham’s one and only son (Gen 22:2, 12, 16). Yet the apostle completely ignores Isaac in favor of a direct connection between Abraham and Christ. The Galatians are related to Abraham through Christ and not through membership in the Jewish people mediated by Isaac.
The Amateur Exegete 