Who was God dealing with between Abraham and Christ?

Les explains that from Abraham until Christ comes in His earthly ministry, God's dealings were almost exclusively with the nation of Israel, with only occasional exceptions toward Gentiles. God called Abram out of Ur, promised him that a nation would come from him through the Abrahamic covenant, and said that through that nation He would consummate His whole plan of redemption. Israel became a nation 500 years later, came out of Egypt under Moses, and received the Law. The Old Testament makeup is Israel under the Law with the priesthood and temple worship, including the Babylonian captivity and the later return under Ezra to set the stage for Israel at Christ's coming.