Read Ellen G. White, “The Law and the Covenants,” pp. 363-373, in Patriarchs and Prophets . “But if the Abrahamic covenant contained the promise of redemption, why was another covenant formed at Sinai? In their bondage the people had to a great extent lost the knowledge of God and of the principles of the Abrahamic covenant
Read more at the source: Friday: Further Study – The Two Covenants