At Sinai, God tells Israel that if they obey His voice and keep His covenant, they will be His treasured possession among all peoples, a kingdom of priests and a holy nation. Moses reminds them that no other nation has such righteous laws or a God who draws near, yet the Song of Moses also warns that Israel would prove unfaithful, chasing after other gods.
That unfaithfulness does not cancel God’s promise, because not all who descend from Israel are true Israel; the true children of Abraham are those united to Christ by faith, Jew and Gentile alike, now built together as living stones into a spiritual house. What Israel was called to be at Sinai, the church becomes in Christ: a chosen race, a royal priesthood, a holy nation, called out of darkness into God’s marvelous light.