Genesis 12:3, “…in you all the families of the earth shall be blessed.”
These are the climactic words of YHWH’s initial covenant promise to Abram in Genesis 12. With these words the entire “History of Redemption” proper gets started. Through Abraham will come Israel, through Israel will come Judah, through Judah will come David and the line of kings, and through David will come the Messiah–who is God With Us–and through the revelatory redemption of the Messiah, all peoples will be drawn into fellowship with the One True God (Ephesians 2:14-18).
This is why, in Galatians 3:8, Paul cites Genesis 12:3 and calls it a fore-preaching of the gospel. In that covenant promise to Abram–the patriarchal “root” of God’s people–was the good news about the Offspring of the woman, of Abraham, Isaac, Jacob, and David, who would crush the serpent and gather God’s people into one by being lifted up as the curse-bearing Lord of love. In Christ alone all nations of the earth are grafted in and become fellow sharers in the blessings of the One People of YHWH God.