Covenant is a term central to the whole of Scripture in which all the Bible finds its clarity. This work shows the reader the relationship between God’s first covenants in the Old Testament and the new covenant sealed in the blood of Christ. No covenant is ever replaced, but rather all are fulfilled in Jesus who is the covenant personified. This key concept has enormous implications for the way Scripture is read and interpreted. It touches on two of the key issues that have helped to shape the nature of the Church, and continue to affect the witness and perception of the Catholic Church in the world. The first is the relationship with the Jewish People, our spiritual ancestors and first brothers and sisters in faith. The second is the tragic divisions within Christianity and the more serious doctrinal division in the Western Church. Both of these can be addressed in the wonderful covenant of God’s saving power. In his commentary on the Second Vatican Council’s document Nostra Aetate, the then Cardinal Ratzinger presented a lucid summary of the central theological issues arising out of the covenant shared by Jews and Christians alike insisting that the Abrahamic and Christian covenants represent a single movement of God in his work of reconciling humankind. He showed how the work of Christ was and is the fulfillment of God’s promise announced in the covenant with Abraham -‘All the nations of the world shall be blessed through you’ (Gn 12:3). This work is an in-depth study of this thesis.