Galatians 3:16 → Genesis 13:15

Paul's quoted lemma at Galatians 3:16 is καὶ τῷ σπέρματί σου — "and to your seed" — the recipient-dative land-grant formula of Genesis 13:15; 17:8, renewed to Isaac and Jacob at 26:3; 28:13, where MT and LXX agree (the LXX also has it at 24:7, where the Hebrew lacks the "and"). The exegetical act is canonical selection, not a claim about grammatical number: zeraʿ/σπέρμα is a collective that takes singular concord as a matter of course, and Paul himself uses the collective sense at 3:29 ("you are Abraham's seed," with "you" plural). Of all the seed-promises available to him, Paul reaches past the famous blessing-oath (Gen 22:18, which he never uses as a lemma — at 3:8 he quotes the "in you" of Gen 12:3/18:18) to the formula in which the canon names the seed, alongside Abraham, as the promise's recipient — because a promise addressed to one heir is precisely the argument he is building: Gal 3:18-29 runs on inheritance and heirs and lands on "heirs according to the promise" (3:29). The canon itself narrows its own term by divine speech (Gen 21:12; 49:10; 2 Sam 7:12-16), and Paul reads that narrowing christologically: the promise-bearing line terminates in one Descendant, Christ, and all who are in corporate union with him inherit with him. The law "was added because of transgressions, until the arrival of the seed to whom the promise referred" (3:19); the Galatians aspire to be in Abraham's fold, and that is true only of those united to the Seed.