How are the new and Old Testaments different?

In summary, the Old Testament lays the foundation for, and was meant to prepare the Israelites for, the coming of the Messiah who would sacrifice Himself for the sins of the whole world (1 John 2:2). The New Testament shares the life of Jesus Christ and then looks back on what He did and how we are to respond to His gift of eternal life and live our lives in gratitude for all He has done for us (Romans 12). Both testaments reveal the same holy, merciful, and righteous God who must condemn sin but who desires to bring to Himself a fallen human race of sinners through the forgiveness only possible through Christ's atoning sacrifice. In both testaments, God reveals Himself to us and how we are to come to Him through Jesus Christ. In both testaments, we find all we need for eternal life and godly living (2 Timothy 3:15-17).