Ancient Messiah Discourse and Paul's Expression ἄχρις οὗ ἔλθῃ τὸ σπέρμα in Galatians 3.19

In Gal 3.16 Paul asserts that Abraham's seed is the messiah. While some have suggested that the rationale for this assertion is Paul's identification of Abraham's seed with David's seed, few have identified evidence for this rationale in the immediate context of Galatians 3, and none have genuinely argued for it. Noting that the reappropriation of scriptural idioms is a common feature of ancient messiah discourse, I demonstrate that Gal 3.19 entails a reappropriation of the wording of Gen 49.10, an oracle often interpreted as Davidic-messianic, and thereby I elucidate the scriptural reasoning undergirding Gal 3.16.