12 Days Bible
God has given us His Word which is two words. One looking forward to the fulfillment of a promise. The other looking back and applying the fulfilled promise to our daily lives. Of course I'm talking about the Old and New Testaments. The complete revelation of what is necessary to know about the promise regarding God's "partridge in a pear tree."
Both testaments hinge around Jesus' death and resurrection. Their anchor are the four Gospels. These tell the story of Jesus' life, death and resurrection in history. We have three readings in our traditional Divine Services so that we heard from all of them. The Old Testament about the promise. The New Testament for what the promise means to us. The Gospels for the promise fulfilled. These tell the whole story of the history of man and his need for God.
Both testaments are necessary for faith to be built up properly. Many want to claim that they are "New Testament Christians" and have no need for the Old Testament. Some who have this outlook want to follow Marcion with his idea that the God of the Old Testament is a different god than the God of the New Testament. God seems jealous and vengeful in the Old Testament. God is love in the New Testament. They don't want to think about one God being both.
But how does St. John see God in Revelation? "He who sat there [on the throne] was like a jasper and sardius stone in appearance" (Revelation 4:3). God is both jealous and vengeful against those who refuse Him, but He is loving and gracious to those who seek to follow Him. Fun fact: Our great Lenten emphasis sung often instead of the Alleluia: "Return to the LORD your God, for He is gracious and merciful, slow to anger, and abounding in steadfast love"; comes from the Old Testament instead of the New.
Both testaments are centered in the Gospel of Jesus Christ. God shows His grace and mercy in both testaments because He is both holy and righteous. His holiness does not allow sin in His presence. His righteousness promised a way for His fallen creatures to be redeemed and be able to live in His presence forever. Amen.