New Defender's Study Bible Notes
3:16 to thy seed. In his theological argument concerning the Abrahamic covenant, Paul almost unconsciously, as it were, makes an exceedingly strong affirmation of the verbal inspiration of the Old Testament Scriptures, basing his argument not just on one word, but one letter, “seed” instead of “seeds.” Thus the promised “Seed” was not the nation Israel, but the one Person who alone could fulfill the great promises made to Abraham, namely, Christ (see Genesis 22:17-18).
3:17 four hundred and thirty years. The 430 years from the Abrahamic promise until the giving of the law to Moses and the 430 years of Israel’s extended stay in Egypt (Exodus 12:40) parallel each other, provided that the reference to “the covenant” here in Galatians 3:17 refers to the final ratification of this covenant, as confirmed to Jacob just as he and his family were leaving Canaan for Egypt (Genesis 46:1-4). This seems quite reasonable in the context of Paul’s argument; see also the comments on Acts 7:6 and Genesis 15:13.