The Old Testament is revelation and law from God covering about the time from the creation of the earth to the time of Jesus' death on the cross. The New Testament is revelation and law from God covering about the time from Jesus' birth to His (future) second coming. It tells us that His Son, Jesus, came, lived, died, and arose so that believers on Jesus as the Christ might have eternal life. The New Testament also tells us, by both command and recorded example how we are to worship God today. The two portionscf God's will are so closely related it can be said about them that the Old is the New concealed and the New is the Old revealed. The Old Testament was preparatory, temporary, and limited. The New is complete, eternal, and universal. The Old Testament promised a New Testament (Jer. 31:31). The prophet Isaiah spoke of the days to come when the new law would go forth from Jerusalem (Isaiah 2:2-4). In the New Testament, the Apostle Paul stated that the law of Moses had been given until the seed, which is Christ Jesus, had come (study Galatians 3:19-27).
The New Testament is the will of Christ, its seal is Jesus' blood (Hebrews 9:15-17). The testator of this will is Jesus, God's Son. The inheritance is heaven. The terms are faith and obedience. The period of probation is the Christian age which will end when Christ returns. The beneficiaries are all men who accept the terms, and the executors of the will are the apostles.
This will could not come of force until Jesus' death, "For where a testament is, there must of necessity be the death of him that made it" Hebrews 9:16. Jesus' death marked the end of the old and the beginning of the new, for, "He taketh away the first that He may establish the second" Hebrews 10:9. Christians are discharged from the law and joined to Christ (Romans 7:4-6).